Ken Costa and I take in the pink marbled splendour of The Ritz Restaurant in London. The winter sun streams through the window behind us. In the distance, a pianist tinkles away at “Goodbye Yellow Brick Road”. “So you bought this place?” I say. “My very good friends and clients did,” he says – his very good friends and investment banking clients being the Barclay twins, Sir David and Sir Frederick, who bought The Ritz in 1995. “I rather like supporting clients. I think it’s always useful, you know.”

It was the great City of London figure Sir Siegmund Warburg who taught Costa the secret of investment banking. “He always used to say, ‘First make a person your friend and then become his banker.’ In many ways, that’s the right way round, and not often practised in this demanding world,” he says. Costa has become banker to many other friends since, including Sweden’s Wallenberg family and South Africa’s Oppenheimers.