Sir Don is rated the greatest batsman of all time

It was bought by an unnamed businessman at an auction in London and the sum paid is believed to be a record for a piece of Bradman memorabilia.

Sir Don wore the cap during the 1947-48 series against India, during which he made his 100th first-class century.

"Anything that is linked to Bradman now sells at a large premium," said Richard Mulvaney, curator of the Bradman Museum.

Sir Don scored 6,996 runs in 52 tests at an average of 99.94.

His average would have been over 100 had he scored four runs in his final Test at the Oval in 1948, but he was bowled for a duck second ball by England's Eric Hollies.

He was knighted the following year and went on to become a cricket administrator and selector in Australia, as well as writing about the game.

Sir Don died in February 2001 at the age of 92, prompting a period of national mourning in Australia.

His memorial service was attended by Prime Minister John Howard, along with numerous cricket greats including Sir Viv Richards, Richie Benaud and Greg Chappell and broadcast live on TV.

It is thought the buyer of Sir Don's cap eventually plans to put it on public display in Australia.