Jean Kierans, now a 65-year-old pensioner, fell in love with Major in 1965 when she was a schoolteacher and he was just 22 and struggling to start a career in banking.
But their four-year affair was doomed because of the 13-year age difference, his political ambitions and the disapproval of Major's mother.
"He has been the love of my life, yes. It was just passion with my first husband, but with John it was everything," Kierans told the Daily Mail newspaper.
British tabloids have portrayed Kierans as the sophisticated divorcee and Major as her "toyboy" lover since the men's magazine Esquire reported the romance. But Kierans claims their roles were very different.
"I was very young for my age, innocent really, and he was very experienced," she said, adding that Major had instigated the first kiss and love on the sofa bed when her children were asleep. "And he was paranoid about me getting pregnant."
Major was also politically ambitious, even at 22, and told her he wanted to be prime minister. "There was never any doubt in his head. It makes me laugh now when I hear him called a grey man. That's just a cover. It's a mask."
Kierans openly admitted her love for Major whom she affectionately referred to by the pet name, Roves.
The greatest stumbling block to a future together was Major's mother. "She liked me as a person and she liked the kids. She liked the set-up for what it was, but when she realized exactly how old I was she just said: 'You marry her over my dead body.'"
News of the affair has made Major, usually portrayed by the media as dour, appear a little more exciting. His life before he married his present wife Norma in 1970 was presumed to be uneventful.
As Britain's leader, Major is often portrayed as lurching from one problem to another and struggling to keep the divided Conservative party together.
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