Trade and Other Payables - Summary of Trade and Other Payables (Details) - GBP (£) £ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Trade And Other Current Payables [Abstract]
Trade payables	£ 4,065	£ 2,285
Social security and other taxes	318	1,107
Accruals and other payables	6,215	4,800
Corporate income tax payable	185
Total trade and other payables	£ 10,783	£ 8,192

The amount of current accrued expenses and other current liabilities. [Refer: Accruals; Other current liabilities]

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 1
-IssueDate 2021-01-01
-Paragraph 55
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=1&code=ifrs-tx-2021-en-r&anchor=para_55&doctype=Standard
-URIDate 2021-03-24

+ Details

Name:	ifrs-full_CurrentAccruedExpensesAndOtherCurrentLiabilities
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The amount of current payables on social security and taxes other than incomes tax. [Refer: Payables on social security and taxes other than income tax]

+ References

+ Details

Name:	ifrs-full_CurrentPayablesOnSocialSecurityAndTaxesOtherThanIncomeTax
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- References

No definition available.

+ Details

Name:	ifrs-full_TradeAndOtherCurrentPayablesAbstract
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The current amount of payment due to suppliers for goods and services used in entity's business. [Refer: Current liabilities; Trade payables]

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 1
-IssueDate 2021-01-01
-Paragraph 78
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=1&code=ifrs-tx-2021-en-r&anchor=para_78&doctype=Standard
-URIDate 2021-03-24

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Name IAS
-Number 1
-IssueDate 2021-01-01
-Paragraph 70
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=1&code=ifrs-tx-2021-en-r&anchor=para_70&doctype=Standard
-URIDate 2021-03-24

+ Details

Name:	ifrs-full_TradeAndOtherCurrentPayablesToTradeSuppliers
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The amount of trade payables and other payables. [Refer: Trade payables; Other payables]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 1
-IssueDate 2021-01-01
-Paragraph 54
-Subparagraph k
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=1&code=ifrs-tx-2021-en-r&anchor=para_54_k&doctype=Standard
-URIDate 2021-03-24

+ Details

Name:	ifrs-full_TradeAndOtherPayables
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Corporate income tax payable.

+ References

No definition available.

+ Details

Name:	sln_CorporateIncomeTaxPayable
Namespace Prefix:	sln_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant