Anthony Gaskell, 69, crossed the finishing line this year in just three hours and five minutes, reports the Daily Mail.
Observers questioned, however, how a previously unknown veteran could have performed so well.
Plans to award Mr Gaskell a plaque to mark his record time were abandoned after analysis of the second half of his race.
Officials worked out he would have had to have run the last 13 miles in under an hour – a time that world record holder, Haile Gebrselassie, could not match.
He appears to have used a part of the course just after Tower Bridge – where the marathon doubles back on itself – to cut from the outward leg to the home leg, taking around ten miles off the course.
Mr Gaskell, a grandfather from the Wirral, Merseyside, insists he never claimed to have run the last part of the course.
“I simply walked through a short cut to the end of the course where my belongings were waiting for me. I had no idea that anyone thought I’d won.”
Colin Rathbone, 66, who finished 38 seconds behind Mr Gaskell after completing the full 26 miles and 385 yards will now receive the fastest pensioner’s plaque.
Mr Rathbone, from Northwich in Cheshire, said: “It was the best time in ten years. When I was told I had been beaten I thought, ‘What the heck do you have to do to win this thing?’.”Post published in: News