A man has cashed in a Grand National-winning bet 43 years late after finding the slip while clearing a house.

Bob Holmes discovered it while helping sort through his late father-in-law's paperwork.

The £1 win-only bet backed Red Rum in the 1974 Grand National, which the famous racehorse won.

It is thought to be a record for the oldest bet ever cashed in.

Red Rum competing in the 1974 Grand National (Bob Thomas/Getty)

Mr Holmes, 76, contacted bookmaker William Hill and it confirmed the slip, placed at odds of 11-1, had never been cashed.

It agreed to pay out on the bet, adjusted for inflation, meaning Mr Holmes gets £130 as well as £130 to place on Saturday's Grand National - plus a matching donation to his favourite charity WaterAid.

Mr Holmes, who lives in Houston, Renfrewshire, said: "My sister-in-law Rhoda Robertson was moving house and my wife and I were helping her to see what could be thrown out, so I was looking through a whole pile of old papers, tax returns, bank statements and so on.

"I came across a scruffy bit of paper that turned out to be a betting slip that had been placed but never cashed.

"When I looked more closely it was for Red Rum in the 1974 Grand National.

"I contacted William Hill who said yes, it is a bet that has been properly placed and they would not only honour it but would increase the value to today's prices."

The famous race horse crosses the finish line 42-years ago (Getty)

The betting slip reads: "£1 win. Red Rum. Live 3.15."

Mr Holmes does not know why his father-in-law Joe Robertson, who died in 1979 aged 82, never cashed in the slip.

He said: "It is a mystery. My father-in-law probably lost the betting slip and was not able to cash it. It would have been worth £12 which was a lot of money at that time, a week's wages for a low paid worker.

"It was very rare for him to bet. He was not a betting man, maybe a couple of times a year on the National or the Derby."

The son of the racehorse trainer, Donald McCain, feeding carrots to Red Rum in '74 (Getty)

Mr Holmes, who worked for the Foreign Office before retiring, sent the slip to William Hill so it could verify its authenticity.

It confirmed the bet was placed at its Paisley branch, which no longer exists, and had never been cashed.

Mr Holmes has split the money William Hill gave him to put on this year's National three ways with his wife Nancy and sister-in-law.

He is backing Blaklion, while his wife has chosen Definitely Red and her sister Ucello Conti.

William Hill spokesman Graham Sharpe said: "It is certainly a record. I've worked at William Hill for 45 years and the record before was seven years for a lady whose husband had passed away and she had not felt able to go through his clothes until then, and had found a betting slip.