The George Medal awarded to a former heavyweight boxer for helping to thwart an attempted kidnap of the Princess Royal has sold for £50,000 at auction.

Former heavyweight boxer Ronnie Russell, 72, punched Ian Ball twice in the head as he tried to kidnap Anne at gunpoint in central London in March 1974.

For his bravery, he was awarded the George Medal by the Queen, who told him: "The medal is from the Queen, but I want to thank you as Anne's mother."

Mr Russell, who now lives in Bristol, has treasured the medal ever since but put it up for auction to pay for his funeral costs after suffering ill-health.

It was expected to fetch up to £20,000 when it went under the hammer at Dix Noonan Webb in central London on Wednesday but instead reached £50,000 - more than twice the estimate.

The medal was bought by a private collector in the UK.

Speaking after the auction, Mr Russell said: "For something I thought that I would never sell, I never believed it would sell for this amount."I am absolutely blown away with this price and gives me opportunities to do things that I thought I never thought we could."

Ball had blocked the princess's car with his own as it drove along the Mall back to Buckingham Palace and fired a series of shots through the rear window as he tried to kidnap the princess.

The princess and her then husband, Captain Mark Phillips, were unhurt during the late-night ambush.

But her personal detective, chauffeur, a police constable and a journalist were all shot by Ball, who was armed with two revolvers.

Mr Russell was then a 28-year-old 6ft 2in 17-stone former boxer who trained at the same club as the Kray twins in Bethnal Green.

He was heading home to Kent when he saw the incident unfold and rushed to the newly-married couple's aid.

He recalled how Anne told Ball "Just go away and don't be such a silly man" as he tried to drag her from the car."I hit him as hard as I could - if he had been a tree he would have fallen over - and he was flat on the floor face down," Mr Russell said.

"Pc Edmonds then dived on top of him and he was arrested."

Ball was later sent to a psychiatric hospital by an Old Bailey judge.