Lee.
Asking for proof of source has been part of the international anti-money laundering efforts for many, many years.
I use MetroBank Remittance Centre in London to transfer funds as required. I transfer online, using the (free) interbank 'FasterPay Service', from my UK bank to the MetroRem centre. MetroRem then direct deposit in our Metrobank account, here in the Bataan. Normally 3 or 4 hours delay, as the UK is either 7 or 8 hours (summer/winter time) adrift from us and the London end transfer to here is done manually. So we go to sleep here and wake up with Pesos in the bank next morning.
If funds are in excess of Stg. 3,000, then (UK) MetroRem "Terms and Conditions" state they 'MAY' ask for proof of source. I was asked a couple of times, about 8 or 9 years ago when we were extending our house and the sums were larger than usual, but nothing since then (touch wood.) We regularly transfer, so have built up a relationship with them and are on first name terms with the manager and the 3 guys who are at the "coal face". Got their personal, UK mobile numbers as well in case of any problems. LOL!
Never had our local branch query any deposits either. Not even when we opened the account with a sizeable cash deposit back in 2006.
Of course, things may be different in other areas!
Peter