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Related Party Disclosures - Additional Information (Detail) - GBP (£)	6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021
Disclosure of transactions between related parties [line items]
Amount paid to trust by the company	£ 0	£ 0
Shares purchased by the EBT	0	0
Cash held by employee benefit trust	£ 17,741		£ 17,866
Repayment of debt by Employee benefit trust		£ 45,493
Ordinary Shares [Member]
Disclosure of transactions between related parties [line items]
Stock Held By Employee Benefit Trust	78,225	145,830

X

- Definition

The amounts payable resulting from related party transactions. [Refer: Related parties [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 24
-IssueDate 2021-01-01
-Paragraph 20
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-URIDate 2021-03-24

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 24
-IssueDate 2021-01-01
-Paragraph 18
-Subparagraph b
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=24&code=ifrs-tx-2021-en-r&anchor=para_18_b&doctype=Standard
-URIDate 2021-03-24

+ Details

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Balance Type:	credit
Period Type:	instant

X

- Definition

The cash inflow from repayment to the entity of loans and advances made to related parties. [Refer: Related parties [member]]

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 7
-IssueDate 2021-01-01
-Paragraph 16
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=7&code=ifrs-tx-2021-en-r&anchor=para_16&doctype=Standard
-URIDate 2021-03-24

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X

- Definition

Line items represent concepts included in a table. These concepts are used to disclose reportable information associated with members defined in one or many axes of the table.

+ References

No definition available.

+ Details

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X

- Definition

Cash held by employee benefit trust.

+ References

No definition available.

+ Details

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Namespace Prefix:	mreo_
Data Type:	xbrli:monetaryItemType
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X

- Definition

Number of shares purchased by entity.

+ References

No definition available.

+ Details

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Balance Type:	na
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- Definition

Stock Held By Employee Benefit Trust.

+ References

No definition available.

+ Details

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Namespace Prefix:	mreo_
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- Details

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