When I banked the other week in Santander for the first time ever the cashier asked where the money was from, I did query why the sudden questioning and she said they have to ask now if it's over £2000, she didn't mention that that was a limit and I was still able to bank the whole amount.
The machine kept rejecting my deposit yesterday so I queued to see the cashier. It was only £900 but the gent did ask where the money came from - I just said my brother gave me money for rent. I asked why he asked and he said that their systems now randomly pings an alert to ask the source of funds due to money laundering. I asked him if my account was specifically flagged and if there was something fishy about me - he emphatically said no - it's just a random thing of the new system; if your personal banking patterns stand out to them, the machine flags you.
Also, I specifically asked about deposit limits and he said that Santander has no limits
at this timeThat means they will probably review the situation in the near future and see how it works out for them and their business model.