Bill Gates would reportedly go on holiday every year with his ex-girlfriend.
The Microsoft founder, who recently announced he is splitting from his wife Melinda, enjoyed regular private getaways with his old flame Ann Winblad.
They would spend a long weekend every year at a beach cottage in North Carolina, US.
The billionaire told Time magazine in 1997 the arrangement was part of the deal when he married Melinda French in 1994.
He said: “We can play putt-putt while discussing biotechnology.”
Bill and Ann began dating in 1984 after meeting at a computer conference and split in 1987, but stayed friends.
He even asked fellow tech fan Ann for her approval before he proposed to Melinda, according to reports.
The tycoon, 65, said: “When I was off on my own thinking about marrying Melinda, I called Ann and asked for her approval.”
Software expert Ann, of Seattle, Washington in the US, said she told him they would be a “good match” as Melinda had “intellectual stamina”.
She is now married to Alex Kline, the detective brother of actor Kevin Kline, according to the New York Post.
Speaking of her trips with Bill, she said: “We share our thoughts about the world and ourselves.”
According to Time magazine, back in 1997 Bill had a photo in his office of himself and Ann on a visit to Germany.
During one trip to Brazil, he took a 1,100-page textbook on molecular biology which they studied together, the magazine reported.
And on another holiday to Santa Barbara, California, they took library movies to “learn more about biotechnology”, Bill said.
Back in 2005, Ann told the San Francisco Chronicle: “Bill wasn’t such a big deal when I started dating him.
“And there was a period of time when my net worth was higher than his, and I had to pay for everything.
“It was a very short period of time, but it was memorable.”
She later claimed Bill told her he could see the way to making $500million (£350million) in revenue during a beach walk while they were dating.
The huge sum was at least five times more than what any other software firm was making at the time.
She said he told her: “What troubles me is I can’t see how I am going to get past $500million.”
In a statement announcing his split from Melinda on Monday, Bill wrote on Twitter: “After a great deal of thought and a lot of work on our relationship, we have made the decision to end our marriage.”
Although they plan to continue their work at the Bill and Melinda Gates Foundation, they “no longer believe we can grow together as a couple in the next phase of our lives”, he added.