From the 1 October 2021, most EU, EEA and Swiss nationals will need to use a valid passport to travel to the UK. ID cards will no longer be accepted as a valid travel document and it will not be possible to enter the UK using them.
This will not apply to EU, EEA and Swiss nationals who have applied to the EU Settlement Scheme by 30 June 2021 or otherwise have protected rights under the Citizens’ Rights Agreements.
This will also not apply to Gibraltar ID cards issued to British citizens or to Irish passport cards which may continue to be used for travel to the UK.
Please link to the GOV.UK site: Visiting the UK as an EU, EEA or Swiss citizen – GOV.UK (www.gov.uk); https://www.gov.uk/guidance/visiting-the-uk-as-an-eu-eea-or-swiss-citizen
British Embassy information