We have heard on a number of occasions, informally, both at my level and at the level of my colleagues who deal exclusively with the CPTPP, about the U.K.'s interest in joining. My understanding is that Secretary of Trade Truss has mentioned it and noted it a few times as well to Minister Ng. I'm not sure of the exact date, but it has been mentioned more than a few times, and as you pointed out, there was the official announcement on that.
On February 5th, 2021. See this statement in context.