It’s the “fairytale underdog story” Hollywood actor Keanu Reeves said simply had to be told on screen.

Ross Brawn convinced the company to allow him to lead a management takeover – nominally buying the team for £1.

Few gave them a chance of being competitive, but in a stunning year Button won the world title and Brawn GP the constructors’ championship.

Reeves goes behind the scenes of that famous season in a new four-part Disney+ documentary series titled Brawn: The Impossible F1 Story.

“It was cool to be able to tell this story,” he told BBC Sport.

Here are six things we learned from the series.

The Brawn GP story is ‘the perfect movie’

Despite the disruption in the build-up to the season, Button won six of the first seven races in 2009.

After a dip in the second half of the season, he clinched the title in dramatic fashion in Brazil – climbing through the field from 14th to finish fifth.

“I could have finished eighth and still clinched the title at the last race by finishing fifth or sixth,” the Briton told BBC Sport. “But I wanted to finish on a high – prove to yourself as much as anyone else that you’ve got that killer instinct.

“Looking back, from not existing as a team to winning our first race, to going on to win five more races, the big dip and the finale – it’s the perfect movie.”

‘Teams either see problems or opportunities’

Formula 1’s governing body the FIA brought in new regulations in 2009 in an attempt to make racing more exciting by increasing overtaking.

Brawn GP concentrated on a section of the car not covered by the new rules, adding an extra hole in a diffuser at the rear. That meant they got more downforce – and therefore more grip on the track – than the rules intended.

As Brawn explains in episode one: “When teams start to look at the design of the cars, they see problems and regulations, or they see opportunities.”

Rival teams protested to the FIA, but the so-called ‘double diffuser’ was ultimately ruled to be legal.

Former Formula 1 CEO Bernie Ecclestone says in episode two that “all the teams, then and now, read the rules, in a different way”.

Brawn’s ‘priceless’ £1 coin travels everywhere

Brawn had masterminded five of the great Michael Schumacher’s seven world championships at Ferrari.

In 2007, he joined Honda as team principal. When they pulled out two years later, he convinced them to allow a management takeover.

Brawn nominally sealed the deal with a pound coin – earning his outfit the nickname ‘The £1 team’.

Honda executive Hiroshi Oshima carries that coin with him wherever he travels.

“That pound is very, very priceless,” he reflects in episode four.

Brawn ‘kept running out of bits’

It is perhaps no surprise given the manner in which the team came together, but Brawn GP were on a tight budget.

As Button reflects, he says that difficult time “brought everyone closer” – but does wish they had more money to spend.

“Every time we damaged the car, we ended up running out of bits,” he told BBC Sport.

The drivers were good friends – but both wanted to win

Barrichello had joined Honda in 2006, having spent five years playing second fiddle to Schumacher at Ferrari.

The Brazilian wasn’t thrilled at the prospect of having to do the same to Button at Brawn GP.

“I was dealing with the fact we could not afford to lose points if we wanted Jenson to win the championship, but I didn’t care about that,” he says in episode three.

“I’m good friends with Jenson, but I wanted to beat him as well.”

Brawn is ‘the most cut-throat, ruthless competitor’

Brawn’s positive public persona does not tally with the experience those who have gone head-to-head with him have had.

“Behind the scenes, he’s the most cut-throat, ruthless competitor probably that we’ve ever come across,” says Red Bull team principal Christian Horner in episode one.

Brawn told BBC Sport he took this as a compliment.

“I used to play rugby,” he said, “and my father always taught me you should be able to smash your competitors on the field and then have a beer afterwards”.