The baggy green cap believed to be worn by Sir Donald Bradman during his innings of 334 in the 1930 Ashes series has been sold for a world record auction price.

An anonymous overseas collector bought Bradman's cap at Christie's in London for STG35,850 ($A95,385).

The buyer beat the previous auction record for an Australian Test cap of STG35,250 ($A93,790) which was paid last year for Bradman's baggy green from the 1946-47 Ashes tour of England.

Bradman's cap from the 1947-48 series against India was sold privately for a sum reportedly over $A200,000 last year in Melbourne.

Christies was adamant the cap sold was the one worn during Bradman's then world record innings of 334 in the third Test at Headingley in Leeds in July, 1930.

"We are certain it is the cap," Christie's specialist Andrew McVinish said.

There is no doubt who the cap belonged to with "D Bradman" inscribed in ink in upper case letters in the lining.

McVinish said a family in Scotland sent the cap to Christie's after hearing of the huge price fetched last year and decided to cash in on the lucrative Bradman memorabilia market.

On his return journey from his first Ashes tour, the 21-year-old Bradman gave his cap to Len Mills, a steward on board the Orient Line ship that took the team on its month-long trip home.

Mills worked for Orient, later P and O, from 1919 to 1967 and retired in his native Scotland where he passed the cap on to his family.

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