The publicity-shy banker has already put down a $5m deposit for the 1,100sq metre (12,000sq ft) flat, which includes a terrace that wraps around the 76th floor of the AOL/Time Warner building and which is still being built.

The property, located in the south tower of the two-tower structure on Columbus circle was sold as a shell - it has no internal walls or decoration - with the estimated cost of doing it up put at a further $5m.

"Whomever he chooses to design it for him is going to have one of the greatest blank spaces in the world," said Pamela Liebman, head of estate agent Corcoran, which acted for the buyer.

New York's previous property record was a $36m Park Avenue pad sold three years ago, but the demand for luxury flats slumped after September 11. It has recently been revived by foreign buyers exploiting the weakening dollar. "The luxury market has recently been bouncing back," broker Roger Erickson told USA Today. "But $45m. That's beyond wow."

Initial rumours that the unknown buyer is an ageing British rock star have been dismissed. "He's not a celebrity. You wouldn't even find him if you did a Google search," said Ms Liebman.