How do I get a 'copy of a cheque'?

Sorry if this is a stupid question, but how do I get a copy of a cheque?

I’m going through the process of encashment of some bonds which I received as inheritance, to do this I need to send over a copy of a cheque to prove my bank details.

Now, I haven’t seen a real cheque book since I was a child, I’ve never had one before, and last I heard they were being phased out here (UK). I’m sure that I can order one from my bank, but what do I need to do with that to make a copy? Do I need to make a payment with a cheque and get a photocopy of it? Who would accept a cheque? Can I do it remotely? These are covid times after all.