Vodka, thank you for replying.
We found out because my Dad's personal banker rang us up on the morning we returned from holiday to say that, while we were away, she'd had a request for an unusually large amount of money to be released from his investments into his current account in order to make a bequest. She had to be a bit cagey because of confidentiality but she was aware that, although I haven't used it yet, there is a power of attorney drawn up (with me as the attorney) so felt she should mention something. And, having known my dad for many years, she felt she had a duty to try and flag up a situation she found a bit unusual. Plus, the person he wanted to give the money too (she wouldn't name by brother, but didn't take much guessing) has already been given sums of money by my dad over the last two years.
The money was for my brother because, in my mum's words, he has been "very good to your father" over the last two years. Two years ago is when my Dad moved into a flat in the grounds of a nursing home owned by my mother and her partner. This home is near the town he has lived in for the last fifty years, the town which was my home town before I left to go to uni, and the town in which my brother and mother still live. Dad did actually come to live with us for about three months but was unhappy being away from familiar territory and all his friends. So this, at the time, their differences having been put behind them, seemed like an ideal solution.
My brother had never got on with my mother's partner, so took to visiting my dad. As far as I can see ( and despite living away now I visited dad very often and spoke Nearly every day - I stayed with him when my parents divorced so we've always been close) "very good" means that my brother took my dad out to lunch in his own car (ie my dad's car) and allowed dad to pay for said lunches. Brother is 38, lives at home, has no dependants, pays for absolutely nothing and has a "job" in the family owned nursing home. So what he actually needs the money for, I'm at a loss to suggest.
In the last 6 weeks or so Dad has deteriorated badly, both physically and mentally. When I told him that he'd written requesting for £40,000 to be released, he had no idea. He trusts my brother, and has got to the stage where, if mum or my brother tell him to sign something, he does. I can't tell you how hurt and upset I am that they would do this to a defenceless old man.