Andrew Clark, 51, had a stockpile of lottery tickets in his Peugeot van.
He discovered the winning ticket in the stash after being urged to check by his partner Trisha Fairhurst.
Mr Clark, from Boston, Lincolnshire, said: “It almost feels like some magical Christmas story, the man who nearly lost £76 million!”
Camelot said Mr Clark had made a claim for the prize, the 12th biggest win ever in the UK, last week
Self-employed Mr Clark said Ms Fairhurst “kept telling me to check the tickets, and her niece Louise, who I was building an extension for, was also in on it once she’d heard about the unclaimed prize in the news”.
“It was something of a standing joke that I had all these tickets while there was a local prize outstanding, so for weeks they were on at me to check,” he added.
He now plans to hang up his trowel and take early retirement.
Grandfather-of-three Mr Clark revealed himself as the winner at a press conference in Grantham earlier.
The ticket was bought from Eastwood Road Post Office in Boston.
Mr Clark also told reporters of a previous occasion in the summer when his stash of lottery tickets blew out of his van window.
He said he was relieved “that hadn’t happened again”.
He and Ms Fairhurst, 51, have already bought a new home but Mr Clark said “the best thing about the win is how we can help all our family”.
Mr Clark said: “This Christmas is going to be a quiet affair, but next year will be a different story.”
He said he also planned to celebrate the win with a meal at a restaurant in Skegness on New Year’s Eve.
The winning ticket matched five main numbers and two Lucky Star numbers to win the entire £76,369,806 jackpot in the draw on 2 November.
The numbers were 5, 15, 17, 37, 44 and the Lucky Star numbers were 7 and 11