On Sat, Oct 23, 2021 at 08:24 PM, Guerbetaler wrote:

what is a "NHS COVID certificate"

Health is run separately by each administration in England, Wales, Scotland and Northern Ireland. Residents of each can apply for a certificate confirming their vaccinated status, usually via an app. https://www.nhs.uk/conditions/coronavirus-covid-19/get-digital-covid-pass/