Tenant swap inventory advise

I have 3 tenants in one property. At the end of their tenancy 2 want to stay and 1 wants to be replaced by someone new, another friend of theirs. I’m wondering how this effects the deposit? Presumably they all need to sign a new contract (so the deposit will be released and they’ll pay a new one?) in theory this isn’t an issue but it’s not really possible to do an inventory in a flat full of stuff. Is it possible to get the new guy to join whilst still using the original inventory or is this illegal?
Many thanks.

You have to start everything from scratch; contract, serving documents, right to rent and deposit, smoke alarm check and legioinella assessment.
You have to do a new inventory but to protect yourself ask that the whole house is cleaned before the deposit is returned or deduct charges now otherwise you will end up with a flat being returned in the condition you give it out at this contract and you will have made a loss that you cannot recoup from a future contract deposit.

I agree with A_A. If you don’t do a proper check-out and do a new inventory now, any damage later can too easily be blamed on the outgoing tenant.