Legal action is being considered after bookmakers William Hill failed to hand over £13,300 in alleged winnings following the marathon-running efforts of super-fit pensioner Buster Martin.

The Epping-based charity the Rhys Daniels Trust will benefit from the money if it is ever paid out, after Buster – who claims to be 101 – completed the 26-mile London Marathon in April.

Buster’s employer, Pimlico Plumbers, has called on the services of law firm Mischon de Raya – which has represented Heather Mills McCarthy and Princess Diana – in its fight for the winnings which it claims were rightly won.

The Rhys Daniels Trust is being supported by Buster and his employer. Buster works three days a week for the firm and washes the company’s vans.

Questions have been asked about Buster’s age but Pimlico Plumbers has submitted his passport and naturalisation certificate – which both show his date of birth as September 1, 1906, and the firm says it has also verified Buster’s date of birth through his National Insurance and NHS number.

However William Hill is refusing to pay out until it has seen France-born Buster’s birth certificate, a document which he does not possess.

Pimlico Plumbers boss Charlie Mullins said: “It’s definitely disgusting. They should honour the bet and they are really making out that he’s a liar. Six documents were presented clearly showing his date of birth.”

“Their (William Hill’s) answer is we’re not saying we won’t pay, we will pay it when he produces his birth certificate.”

Two bets were placed on Buster, who came to England from France when he was three months old, before the 26-mile race in April.

Mr Mullins said two £100 bets were laid – that Buster would finish the race in under 12 hours (at odds of 100-1) and that he would finish before midnight (33-1). Buster crossed the finishing line in ten hours exactly.

However William Hill media relations director Graham Sharpe said the bets related to Buster’s supposed age – 101 – and included a £101 stake, with odds of 100-1 that Buster would would finish the race in under 12 hours.

Mr Sharpe said: “We’re just waiting for the proof of Buster’s age (his birth certificate). A passport is only proof of nationality and a naturalisation certificate is likewise. Most of that is self-certification.

“We rang the French Embassy and said it appeared there was some confusion. They were very insulted and said ‘do you think we are a medieval country and we don’t have birth certificates?’.”

Mr Sharpe added: “He was put up to us as the oldest man to ever complete the London Marathon and he’s not even that unless he can prove he is 98. The whole point of the bet was that he was 101 and no-one has proved the point that he is.”

Barry Daniels, founder of the Rhys Daniels Trust, said: “I think they’re back-tracking. They (Pimlico Plumbers) have done everything above board. They could have paid the money out. They accepted the bet based on their conditions.

“I think it’s appalling that they’re making a big deal out of this which is causing a lot of work for Pimlico Plumbers and at the end of the day the charity is losing out.”

A letter from William Hill to Mischon de Raya said any legal action would be “robustly defended”.