Bill Gates maintained an unusual relationship with his ex-girlfriend for years after they split - and wife Melinda approved the arrangement.

Gates remained close to ex Ann Winblad and would spend a long weekend with her every year for at least a decade.

A story in Time magazine details how the Microsoft founder dated fellow tech entrepreneur Winblad for three years after they met at a tech conference. The pair began a 1980s-style virtual relationship that involved them going to the same movie at the same time in different cities and then discussing it on their proto-mobile phones.

They eventually split despite Winblad's readiness for marriage, because of Gates' devotion to his work.

But Winblad remained important to Gates - who even called his ex to ask for approval to propose to Melinda.

"When I was off on my own thinking about marrying Melinda," Gates told the magazine, "I called Ann and asked for her approval."

Ann Winblad in 1984. Photo / Getty Images

Winblad approved the union because, she said, Melinda had the "intellectual stamina" to keep up with her ex-beau.

The 1997 Time magazine profile spilled the beans on the former lovers' tradition, writing that the "kindred spirits" travelled extensively while they were together and held on to that one weekend after their split.

At Winblad's North Carolina beach cottage the pair would "ride dune buggies, hang-glide and walk on the beach".

"We can play putt-putt while discussing biotechnology," Gates said, with Winblad revealing: "We share our thoughts about the world and ourselves".

"And we marvel about how, as two young overachievers, we began a great adventure on the fringes of a little-known industry and it landed us at the centre of an amazing universe."

The arrangement even saw the trio spending time together, with Time telling how they decamped to a secluded resort in New York State to ... play with 1000-piece jigsaw puzzles.

Bill Gates and his wife Melinda announced their split yesterday, after 27 years of marriage.

"After a great deal of thought and a lot of work, we have made the decision to end our marriage. Over the last 27 years, we have raised three incredible children and built a foundation that works all over the world to enable all people to lead healthy, productive lives," the couple said.

"We continue to share a belief in that mission and will continue to work together at the foundation, but we no longer believe we can grow together as a couple in this next phase of our lives.

"We ask for space and privacy for our family as we begin to navigate this new life."

The couple have three children; Jennifer, 25, Rory, 21, and Phoebe, 18.

They have amassed a fortune of US$127 billion.

Bill and Melinda got married on New Year's Day in 1994, in a private ceremony in Hawaii.

In 2000, they launched the Bill & Melinda Gates Foundation, with ambitious goals that included the reduction of extreme poverty around the world.

This past year, it was heavily involved in the world's response to Covid-19, committing $1.75b to help develop and distribute vaccines.

The couple met in 1987, when Melinda - then known as Melinda French - was a product manager at Microsoft.

In a Netflix documentary series a couple of years ago, Melinda shared an amusing anecdote from about one year into their relationship, when she walked in on Bill as he was drawing up a list of the "pros and cons" of getting married.

"He had to make a decision," she said, bursting into laughter.

At first, the pair revealed, their relationship was a casual one.

"She had other boyfriends, and I had Microsoft," said Bill.

"We were like, 'Hey we are not really serious about each other, are we? We are not going to demand each other's time'."

"I was new to Microsoft, there were a lot of men there, and you are still looking around," Melinda added.

After a year, though, to their own surprise, they decided they loved each other.

When they finally got married in 1994, he was 38 and she was 29.