
Santander does more than £30,000 over the phone, at no charge. I have done this before. It involved them having to call me back to confirm I really meant it but the payment was made on the same day. You could probably also set up a one-off standing order for £30,000.

All banks are likely to make extra checks when a one-off large payment gets made. You'd expect them to. Or may be you wouldn't, but I would
