| 
             Page 
           | 
        ||
| 
             2 
           | 
        ||
| 
             3 
           | 
        ||
| 
             4 
           | 
        ||
| 
             5 
           | 
        ||
| 
             6 
           | 
        
| 
             Three months ended 
            March 31, 
           | 
          ||||||||||||
| 
             Notes 
           | 
          
             2022 
            £’000 
           | 
          
             2021 
            £’000 
           | 
          ||||||||||
| 
             Product revenue, net 
           | 
          3  | 
          
             7,682 
           | 
          
             — 
           | 
          |||||||||
| 
             Pre-product revenue, net 
           | 
          3  | 
          
             2,829 
           | 
          
             — 
           | 
          |||||||||
| 
             Collaboration revenue 
           | 
          3  | 
          
             11,963 
           | 
          
             8,270 
           | 
          |||||||||
| 
             Total revenue 
           | 
          
             22,474 
           | 
          
             8,270 
           | 
          ||||||||||
| 
             Cost of product revenue 
           | 
          
             (248 
           | 
          
             ) 
           | 
          
             — 
           | 
          |||||||||
| 
             Research and development costs 
           | 
          
             (18,581 
           | 
          
             ) 
           | 
          
             (19,885 
           | 
          
             ) 
           | 
        ||||||||
| 
             Selling and administrative expenses 
           | 
          
             | 
          
             (20,106 
           | 
          
             ) 
           | 
          
             (20,184 
           | 
          
             ) 
           | 
        |||||||
| 
             Net other operating income / (expense) 
           | 
          
             1 
           | 
          
             (82 
           | 
          
             ) 
           | 
        |||||||||
| 
             Operating loss 
           | 
          
             (16,460 
           | 
          
             ) 
           | 
          
             (31,881 
           | 
          
             ) 
           | 
        ||||||||
| 
             Finance income 
           | 
          
             10 
           | 
          
             22 
           | 
          ||||||||||
| 
             Finance costs 
           | 
          
             4 
           | 
          
             (1,333 
           | 
          
             ) 
           | 
          
             (1,860 
           | 
          
             ) 
           | 
        |||||||
| 
             Non-operating expense 
           | 
          
             (1,323 
           | 
          
             ) 
           | 
          
             (1,838 
           | 
          
             ) 
           | 
        ||||||||
| 
             Loss before taxation 
           | 
          
             (17,783 
           | 
          
             ) 
           | 
          
             (33,719 
           | 
          
             ) 
           | 
        ||||||||
| 
             Income tax credit 
           | 
          
             5 
           | 
          
             1,655 
           | 
          
             4,681 
           | 
          |||||||||
| 
             Loss for the period 
           | 
          
             (16,128 
           | 
          
             ) 
           | 
          
             (29,038 
           | 
          
             ) 
           | 
        ||||||||
| 
             Other comprehensive income / (loss) 
           | 
          ||||||||||||
| 
             Other comprehensive income / (loss) that is or may be reclassified to profit or loss in subsequent periods: 
           | 
          ||||||||||||
| 
             Exchange differences on translation of foreign operations 
           | 
          
             205 
           | 
          
             (92 
           | 
          
             ) 
           | 
        |||||||||
| 
             Total other comprehensive income / (loss) for the period 
           | 
          
             205 
           | 
          
             (92 
           | 
          
             ) 
           | 
        |||||||||
| 
             Total comprehensive loss for the period 
           | 
          
             (15,923 
           | 
          
             ) 
           | 
          
             (29,130 
           | 
          
             ) 
           | 
        ||||||||
| 
             Basic and diluted loss per share - £ 
           | 
          6 | 
             (0.37 
           | 
          
             ) 
           | 
          
             (0.76 
           | 
          
             ) 
           | 
        |||||||
| 
             Notes 
           | 
          
             March 31, 
            2022 
            £’000 
           | 
          
             December 31, 
            2021 
            £’000 
           | 
          ||||||||||
| 
             Non-current assets 
           | 
          ||||||||||||
| 
             Property, plant and equipment 
           | 
          
             7,849 
           | 
          
             8,944 
           | 
          ||||||||||
| 
             Right of use assets 
           | 
          
             22,199 
           | 
          
             22,593 
           | 
          ||||||||||
| 
             Other non-current assets 
           | 
          
             5,955 
           | 
          
             4,935 
           | 
          ||||||||||
| 
             Deferred tax asset 
           | 
          
             2,650 
           | 
          
             2,575 
           | 
          ||||||||||
| 
             Total non-current assets 
           | 
          
             38,653 
           | 
          
             39,047 
           | 
          ||||||||||
| 
             Current assets 
           | 
          ||||||||||||
| 
             Inventory 
           | 
          
             496 
           | 
          
             — 
           | 
          ||||||||||
| 
             Trade and other receivables 
           | 
          
             7 
           | 
          
             25,746 
           | 
          
             15,208 
           | 
          |||||||||
| 
             Tax receivable 
           | 
          
             11,289 
           | 
          
             9,632 
           | 
          ||||||||||
| 
             Cash and cash equivalents 
           | 
          
             205,853 
           | 
          
             237,886 
           | 
          ||||||||||
| 
             Total current assets 
           | 
          
             243,384 
           | 
          
             262,726 
           | 
          ||||||||||
| 
             Total assets 
           | 
          
             282,037 
           | 
          
             301,773 
           | 
          ||||||||||
| 
             Equity 
           | 
          ||||||||||||
| 
             Share capital 
           | 
          
             88 
           | 
          
             88 
           | 
          ||||||||||
| 
             Share premium 
           | 
          
             212,499 
           | 
          
             212,238 
           | 
          ||||||||||
| 
             Foreign currency translation reserve 
           | 
          
             294 
           | 
          
             89 
           | 
          ||||||||||
| 
             Other reserves 
           | 
          
             386,167 
           | 
          
             386,167 
           | 
          ||||||||||
| 
             Share-based payment reserve 
           | 
          
             61,770 
           | 
          
             54,357 
           | 
          ||||||||||
| 
             Accumulated deficit 
           | 
          
             (497,520 
           | 
          
             ) 
           | 
          
             (481,392 
           | 
          
             ) 
           | 
        ||||||||
| 
             Total equity 
           | 
          
             163,298 
           | 
          
             171,547 
           | 
          ||||||||||
| 
             Non-current liabilities 
           | 
          ||||||||||||
| 
             Interest-bearing loans and borrowings 
           | 
          
             38,370 
           | 
          
             37,226 
           | 
          ||||||||||
| 
             Deferred revenue 
           | 
          
             3 
           | 
          
             2,136 
           | 
          
             6,408 
           | 
          |||||||||
| 
             Lease liabilities 
           | 
          
             25,043 
           | 
          
             25,355 
           | 
          ||||||||||
| 
             Provisions 
           | 
          
             70 
           | 
          
             57 
           | 
          ||||||||||
| 
             Total non-current liabilities 
           | 
          
             65,619 
           | 
          
             69,046 
           | 
          ||||||||||
| 
             Current liabilities 
           | 
          ||||||||||||
| 
             Trade and other payables 
           | 
          
             9 
           | 
          
             34,695 
           | 
          
             35,436 
           | 
          |||||||||
| 
             Deferred revenue 
           | 
          
             3 
           | 
          
             17,089 
           | 
          
             24,450 
           | 
          |||||||||
| 
             Lease liabilities 
           | 
          
             1,294 
           | 
          
             1,255 
           | 
          ||||||||||
| 
             Provisions 
           | 
          
             42 
           | 
          
             39 
           | 
          ||||||||||
| 
             Total current liabilities 
           | 
          
             53,120 
           | 
          
             61,180 
           | 
          ||||||||||
| 
             Total liabilities 
           | 
          
             118,739 
           | 
          
             130,226 
           | 
          ||||||||||
| 
             Total equity and liabilities 
           | 
          
             282,037 
           | 
          
             301,773 
           | 
          ||||||||||
| 
             Notes 
           | 
          
             Share 
            capital 
            £’000 
           | 
          
             Share 
            premium 
            £’000 
           | 
          
             Foreign 
            currency 
            translation 
            reserve 
            £’000 
           | 
          
             Share- 
            based 
            payment 
            reserve 
            £’000 
           | 
          
             Other 
            reserve 
            £’000 
           | 
          
             Accumulated 
            deficit 
            £’000 
           | 
          
             Total 
            equity 
            £’000 
           | 
          |||||||||||||||||||||||||
| 
             At January 1, 2022 
           | 
          
             88 
           | 
          
             212,238 
           | 
          
             89 
           | 
          
             54,357 
           | 
          
             386,167 
           | 
          
             (481,392 
           | 
          
             ) 
           | 
          
             171,547 
           | 
          ||||||||||||||||||||||||
| 
             Loss for the period 
           | 
          
             — 
           | 
          
             — 
           | 
          
             — 
           | 
          
             — 
           | 
          
             — 
           | 
          
             (16,128 
           | 
          
             ) 
           | 
          
             (16,128 
           | 
          
             ) 
           | 
        |||||||||||||||||||||||
| 
             Other comprehensive income 
           | 
          
             — 
           | 
          
             — 
           | 
          
             205 
           | 
          
             — 
           | 
          
             — 
           | 
          
             — 
           | 
          
             205 
           | 
          |||||||||||||||||||||||||
| 
             Total comprehensive income/ (loss) for the period 
           | 
          
             — 
           | 
          
             — 
           | 
          
             205 
           | 
          
             — 
           | 
          
             — 
           | 
          
             (16,128 
           | 
          
             ) 
           | 
          
             (15,923 
           | 
          
             ) 
           | 
        |||||||||||||||||||||||
| 
             Exercise of share options 
           | 
          
             — 
           | 
          
             261 
           | 
          
             — 
           | 
          
             — 
           | 
          
             — 
           | 
          
             — 
           | 
          
             261 
           | 
          |||||||||||||||||||||||||
| 
             Equity-settled share-based payment transactions 
           | 
          
             8 
           | 
          
             — 
           | 
          
             — 
           | 
          
             — 
           | 
          
             7,413 
           | 
          
             — 
           | 
          
             — 
           | 
          
             7,413 
           | 
          ||||||||||||||||||||||||
| 
             At March 31, 2022 
           | 
          
             88 
           | 
          
             212,499 
           | 
          
             294 
           | 
          
             61,770 
           | 
          
             386,167 
           | 
          
             (497,520 
           | 
          
             ) 
           | 
          
             163,298 
           | 
          ||||||||||||||||||||||||
| 
             Notes 
           | 
          
             Share 
            capital 
            £’000 
           | 
          
             Share 
            premium 
            £’000 
           | 
          
             Foreign 
            currency 
            translation 
            reserve 
            £’000 
           | 
          
             Share- 
            based 
            payment 
            reserve 
            £’000 
           | 
          
             Other 
            reserve 
            £’000 
           | 
          
             Accumulated 
            deficit 
            £’000 
           | 
          
             Total 
            equity 
            £’000 
           | 
          |||||||||||||||||||||||||
| 
             At January 1, 2021 
           | 
          
             64 
           | 
          
             — 
           | 
          
             163 
           | 
          
             18,821 
           | 
          
             386,167 
           | 
          
             (349,869 
           | 
          
             ) 
           | 
          
             55,346 
           | 
          ||||||||||||||||||||||||
| 
             Loss for the period 
           | 
          
             — 
           | 
          
             — 
           | 
          
             — 
           | 
          
             — 
           | 
          
             (29,038 
           | 
          
             ) 
           | 
          
             (29,038 
           | 
          
             ) 
           | 
        ||||||||||||||||||||||||
| 
             Other comprehensive loss 
           | 
          
             — 
           | 
          
             — 
           | 
          
             (92 
           | 
          
             ) 
           | 
          
             — 
           | 
          
             — 
           | 
          
             — 
           | 
          
             (92 
           | 
          
             ) 
           | 
        |||||||||||||||||||||||
| 
             Total comprehensive loss for the period 
           | 
          
             — 
           | 
          
             — 
           | 
          
             (92 
           | 
          
             ) 
           | 
          
             — 
           | 
          
             — 
           | 
          
             (29,038 
           | 
          
             ) 
           | 
          
             (29,130 
           | 
          
             ) 
           | 
        ||||||||||||||||||||||
| 
             Issue of share capital 
           | 
          
             24 
           | 
          
             210,961 
           | 
          
             — 
           | 
          
             — 
           | 
          
             — 
           | 
          
             — 
           | 
          
             210,985 
           | 
          |||||||||||||||||||||||||
| 
             Equity-settled share-based payment transactions 
           | 
          
             8 
           | 
          
             — 
           | 
          
             325 
           | 
          
             — 
           | 
          
             8,271 
           | 
          
             — 
           | 
          
             — 
           | 
          
             8,596 
           | 
          ||||||||||||||||||||||||
| 
             At March 31, 2021 
           | 
          
             88 
           | 
          
             211,286 
           | 
          
             71 
           | 
          
             27,092 
           | 
          
             386,167 
           | 
          
             (378,907 
           | 
          
             ) 
           | 
          
             245,797 
           | 
          ||||||||||||||||||||||||
| 
             Three months ended 
            March 31, 
           | 
          ||||||||
| 
             2022 
            £’000 
           | 
          
             2021 
            £’000 
           | 
          |||||||
| 
             Cash flows from operating activities 
           | 
          ||||||||
| 
             Loss for the period 
           | 
          
             (16,128 
           | 
          
             ) 
           | 
          
             (29,038 
           | 
          
             ) 
           | 
        ||||
| 
             Adjustments for: 
           | 
          ||||||||
| 
             Equity settled share-based payment expense 
           | 
          
             7,413 
           | 
          
             8,596 
           | 
          ||||||
| 
             Depreciation 
           | 
          
             1,679 
           | 
          
             1,807 
           | 
          ||||||
| 
             Net finance costs 
           | 
          
             1,323 
           | 
          
             1,838 
           | 
          ||||||
| 
             Foreign exchange differences 
           | 
          
             945 
           | 
          
             (368 
           | 
          
             ) 
           | 
        |||||
| 
             Other 
           | 
          
             (1 
           | 
          
             ) 
           | 
          
             219 
           | 
          |||||
| 
             Income tax credit 
           | 
          
             (1,655 
           | 
          
             ) 
           | 
          
             (4,681 
           | 
          
             ) 
           | 
        ||||
| 
             Working capital adjustments: 
           | 
          ||||||||
| 
             (Increase) / decrease in receivables and other non-current assets 
           | 
          
             (11,489 
           | 
          
             ) 
           | 
          
             2,068 
           | 
          |||||
| 
             (Decrease) / increase in trade and other payables 
           | 
          
             (807 
           | 
          
             ) 
           | 
          
             631 
           | 
          |||||
| 
             Decrease in deferred revenue 
           | 
          
             (11,633 
           | 
          
             ) 
           | 
          
             (7,051 
           | 
          
             ) 
           | 
        ||||
| 
             Other working capital movements 
           | 
          
             (480 
           | 
          
             ) 
           | 
          
             — 
           | 
          |||||
| 
             Net cash used in operating activities 
           | 
          
             (30,833 
           | 
          
             ) 
           | 
          
             (25,979 
           | 
          
             ) 
           | 
        ||||
| 
             Cash flows from investing activities 
           | 
          ||||||||
| 
             Proceeds from sale of property, plant and equipment 
           | 
          
             5 
           | 
          
             — 
           | 
          ||||||
| 
             Purchase of property, plant and equipment 
           | 
          
             (138 
           | 
          
             ) 
           | 
          
             (220 
           | 
          
             ) 
           | 
        ||||
| 
             Proceeds from investment in sub-leases 
           | 
          
             — 
           | 
          
             245 
           | 
          ||||||
| 
             Net cash flows (used in) / generated by investing activities 
           | 
          
             (133 
           | 
          
             ) 
           | 
          
             25 
           | 
          |||||
| 
             Cash flows from financing activities 
           | 
          ||||||||
| 
             Gross proceeds from issue of share capital 
           | 
          
             — 
           | 
          
             226,528 
           | 
          ||||||
| 
             Costs from issue of share capital 
           | 
          
             — 
           | 
          
             (15,543 
           | 
          
             ) 
           | 
        |||||
| 
             Exercise of share options 
           | 
          
             261 
           | 
          
             — 
           | 
          ||||||
| 
             Interest paid on non-current interest-bearing loan 
           | 
          
             (838 
           | 
          
             ) 
           | 
          
             (810 
           | 
          
             ) 
           | 
        ||||
| 
             Repayment of lease liabilities 
           | 
          
             (755 
           | 
          
             ) 
           | 
          
             (802 
           | 
          
             ) 
           | 
        ||||
| 
             Net cash flows (used in) / generated by financing activities 
           | 
          
             (1,332 
           | 
          
             ) 
           | 
          
             209,373 
           | 
          |||||
| 
             (Decrease) / increase in cash and cash equivalents 
           | 
          
             (32,298 
           | 
          
             ) 
           | 
          
             183,419 
           | 
          |||||
| 
             Net foreign exchange difference on cash held 
           | 
          
             265 
           | 
          
             (52 
           | 
          
             ) 
           | 
        |||||
| 
             Cash and cash equivalents at beginning of the year 
           | 
          
             237,886 
           | 
          
             129,716 
           | 
          ||||||
| 
             Cash and cash equivalents at end of the period 
           | 
          
             205,853 
           | 
          
             313,083 
           | 
          ||||||
| 
             For the three months ended 
            March 31, 
           | 
          ||||||||
| 
             2022 
            £’000 
           | 
          
             2021 
            £’000 
           | 
          |||||||
| 
             Product revenue, net 
           | 
          
             7,682 
           | 
          
             — 
           | 
          ||||||
| 
             Pre-product revenue, net 
           | 
          
             2,829 
           | 
          
             — 
           | 
          ||||||
| 
             Total revenue from sale of therapies 
           | 
          
             10,511 
           | 
          
             — 
           | 
          ||||||
| 
             Collaboration revenue 
           | 
          ||||||||
| 
             GSK 
           | 
          
             — 
           | 
          
             3,370 
           | 
          ||||||
| 
             Eli Lilly 
           | 
          
             7,361 
           | 
          
             — 
           | 
          ||||||
| 
             Genentech 
           | 
          
             4,602 
           | 
          
             4,900 
           | 
          ||||||
| 
             Total collaboration revenue 
           | 
          
             11,963 
           | 
          
             8,270 
           | 
          ||||||
| 
             Total revenue 
           | 
          
             22,474 
           | 
          
             8,270 
           | 
          ||||||
| 
             For the three months ended 
            March 31, 
           | 
          ||||||||
| 
              2022 
           | 
          
             2021 
           | 
          |||||||
| 
             | 
          
             £’000 
             | 
          
             | 
          
             £’000 
           | 
          |||||
| 
             United States 
           | 
          
             7,682 
           | 
          
             — 
           | 
          ||||||
| 
             Europe 
           | 
          
             2,829 
           | 
          
             — 
           | 
          ||||||
| 
             Total revenue from the sale of therapies 
           | 
          
             10,511 
           | 
          
             — 
           | 
          ||||||
| 
             For the three months ended 
            March 31, 
           | 
          ||||||||
| 
             2022 
            £’000 
           | 
          
             2021 
            £’000 
           | 
          |||||||
| 
             Interest expense on lease liabilities 
           | 
          
             429 
           | 
          
             439 
           | 
          ||||||
| 
             Interest expense on financial liabilities measured at amortized cost 
           | 
          
             904 
           | 
          
             1,421 
           | 
          ||||||
| 
             1,333 
           | 
          
             1,860 
           | 
          |||||||
| 
             For the three months ended 
            March 31, 
           | 
          ||||||||
| 
              2022 
           | 
          
             2021 
           | 
          |||||||
| 
             Loss for the period (£’000s) 
           | 
          
             (16,128 
           | 
          
             ) 
           | 
          
             (29,038 
           | 
          
             ) 
           | 
        ||||
| 
             Basic and diluted weighted average number of shares 
           | 
          
             43,865,799 
           | 
          
             38,451,332 
           | 
          ||||||
| 
             Basic and diluted loss per share (£) (1) 
           | 
          
             (0.37 
           | 
          
             ) 
           | 
          
             (0.76 
           | 
          
             ) 
           | 
        ||||
| 
             March 31, 
            2022 
            £’000 
           | 
          
             December 31, 
            2021 
            £’000 
           | 
          |||||||
| 
             Trade receivables 
           | 
          
             16,795 
           | 
          
             6,047 
           | 
          ||||||
| 
             Other receivables 
           | 
          
             2,355 
           | 
          
             1,470 
           | 
          ||||||
| 
             Prepayments and accrued income 
           | 
          
             6,596 
           | 
          
             7,691 
           | 
          ||||||
| 
             25,746 
           | 
          
             15,208 
           | 
          |||||||
| 
             For the three months ended 
            March 31 
           | 
          ||||||||
| 
              
           | 
          
             2022 
            $ 
           | 
          
             2021 
            $ 
           | 
          ||||||
| 
             Weighted average exercise price 
           | 
          
             24.95 
           | 
          
             26.00 
           | 
          ||||||
| 
             Weighted average fair value 
           | 
          
             15.27 
           | 
          
             16.16 
           | 
          ||||||
| 
             March 31, 
            2022 
            £’000 
           | 
          
             December 31, 
            2021 
            £’000 
           | 
          |||||||
| 
             Trade payables 
           | 
          
             6,074 
           | 
          
             7,499 
           | 
          ||||||
| 
             Other taxation and social security 
           | 
          
             733 
           | 
          
             532 
           | 
          ||||||
| 
             Accruals 
           | 
          
             27,680 
           | 
          
             27,382 
           | 
          ||||||
| 
             Other payables 
           | 
          
             208 
           | 
          
             23 
           | 
          ||||||
| 
             34,695 
           | 
          
             35,436 
           | 
          |||||||