How do i legally change my surname? uk based

If you’ve taken your spouse’s surname after marriage, you usually don’t need a deed poll just to start using it. Your marriage certificate is normally the evidence linking your old and new surname, including when updating a British passport.

I found this article useful when I was reading about surname changes and the paperwork involved. It’s written mainly for UK nationals dealing with a name change abroad, but there’s still some useful information on the process and documents:

https://consultantlm.uk/consultant-article/changing-your-surname-abroad-a-uk-nationals-legal-guide