I'd guess they'll ask for a bit more information but it's up to them - it's their livelihood on the line if they're not doing their job properly. I do know tha

I'd guess they'll ask for a bit more information but it's up to them - it's their livelihood on the line if they're not doing their job properly. I do know that I gifted someone buying a house £2k via bank transfer. The solicitor queried it, had me fill out a form saying who I was, why I'd transferred the money, where I'd got the money from and to prove it. I was able to provide them with a statement from a savings account showing a regular amount going in and then £2k being withdrawn and that satisfied them.