As young aspiring racers, Lewis Hamilton and Nico Rosberg were friends for many years as they rose up through the ranks of global motorsport. But that relationship soon soured when they found themselves team mates at Mercedes from 2013.
Rosberg had already been with the team alongside Michael Schumacher ever since Mercedes brought Brawn GP at the end of 2009. At first all was well, but everything changed in 2014 when the squad - and its drivers - became genuine title contenders
“It happened immediately when we were fighting for the world championship, not before,” Rosberg told the German Europsort news channel. "But that’s always the case.
"When you’re fighting for success in every race and for titles, it doesn’t work anymore," he explained. “You have to test limits and go into grey areas to win. Especially when two drivers are at such a high level, it often gets tight.
“If you want to decide the world championship for yourself, you can’t play ‘peace, joy, pancake’," he said, adding that there hadn't been one inciting moment that led to the collapse of their former friendship.
Over the next three seasons, Mercedes' dominance in the championship meant that Hamilton and Rosberg were in an exclusive battle for the driver's title with everyone else much too far behind to challenge.
Hamilton went on to win in 2014 and 2015, but the number of on-track clashes between the pair increased. Behind the scenes the pair found it hard to be civil to each other or even be in the same room.
Both drivers ending up out of the 2016 Spanish GP when they collided on the first lap. Rosberg has since admitted to resorting to 'mind games' during the rest of the season to get the better of Hamilton.
It worked, with the German driver going on to narrowly clinch the title in Abu Dhabi. He then unexpectedly retired from Formula 1 five days later, but insists that he has no regrets about what he did to finally seize the crown.
“I don’t regret anything,” he said. “That was a sensational time and a mega fight. I’m very proud of that."
Although relations between them remained strained for a long time afterwards, they have gradually started to get back on better terms.
Rosberg recounted in May how he and Hamilton had recently had a chance encounter in the lift at their apartment complex in Monaco.
And in a previous interview, Hamilton recalled how it was memories of the times he spent with Rosberg's family as a teenager that had gone on to shape his image of Monaco as a place - and now a home - rather than just a racing venue.
"In the meantime we’ve returned to neutral, which is okay," he said of the current state of his relationship with Hamilton. "And the funny thing is, we are fighting each other again in Extreme E!
"We didn't know about each other's plans beforehand; we built up our racing teams in parallel," he added. "We also announced our teams within a couple of weeks [of each other], which was totally cool.
"It's great that we're reviving this duel."
Rosberg has been working as a commentator and analyst for Sky Sports F1 but was reportedly recently stripped of his champion's all-access paddock pass for refusing to get a COVID vaccination.
Formula 1's current COVID protocols require that any individual - team members, officials or members of the media - entering the paddock must be fully vaccinated.
Rosberg argued that having contracted coronavirus already, he had natural antibodies and immunity. and that his doctor has told him he did not required a vaccine on top.
This year, Rosberg has been working with the Sky team from home.
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