no need for you to inform them of your other accounts with other banks (and privacy laws may forbid banks from sharing this information). The UK have a small

no need for you to inform them of your other accounts with other banks (and privacy laws may forbid banks from sharing this information). The UK have a small number of credit reference agencies, and UK banks universally (as far as I can tell - there may be extremely niche private banks which don't) share customer data with one or more credit reference agencies (and there is provision in law for this). Every bank I know will carry out a credit-check on a customer opening a new account (even an existing customer), so your other accounts will be immediately visible to the bank you're applying to - and the fact of your application will also be recorded. I have no idea how much that information would affect your application, but I'd be extremely surprised if questions weren't asked.