It has long been thought that when Jem Mason won the first Grand National 178 years ago he was proudly sporting the blue silk of one of the most prominent racehorse owners of the day.

But a startling new discovery will force racing aficionados to rewrite the history books.

The original silk jacket worn by Mason when he romped to victory on Lottery has now been unearthed and is revealed to have in fact been a vivid shade of red.

The National Heritage Centre for Horseracing, at Newmarket, acquired Mason’s silk at auction and, after a long and painstaking programme of restoration by textile experts, has put it on public display for the first time.

Most contemporary paintings of Mason show him wearing the blue silk and black cap of racehorse owner John Elmore, leading in later years to the widespread assumption that these were the colours he wore at Aintree, when the first Grand National was held on February 26, 1839.

However, experts now believe the confusion arose because Elmore later changed his colours from the red which Mason wore in that inaugural race to blue.