The gloves are off between Lewis Hamilton and Sebastian Vettel, and Formula One is already the winner.
After so much talk of mutual respect, their previously harmonious relationship melted in the heat of Sunday's hectic Azerbaijan Grand Prix in Baku.
Hamilton said Vettel "disgraced himself" by deliberately driving his Ferrari alongside and swerving it into the side of him. Vettel, who was given a time penalty, said he only did it in response to a dangerous braking move by Hamilton right in front of him.
Whatever the arguments, F1 finally has what it craves: a saga between fiercely competitive champions that promises to last all season.
"Now we've a situation where there is more controversy. It was clear this could happen the closer it gets," Mercedes head of motorsport Toto Wolff said. "(It) certainly doesn't help their relationship going forward. Now the gloves are off."
Hamilton and Vettel have won a combined seven F1 titles and more than 100 races. Vettel has four of those titles, while Hamilton has three. But the British driver has won more races, 56 to 45.
This season they are evenly matched, with three wins each, and Vettel leads Hamilton in the overall championship by 14 points after eight races.
While Hamilton often tangled with former Mercedes teammate Nico Rosberg over the past three years, losing the title to him last year, this new showdown is more intriguing. Not only does it involve multiple world champs — which was not the case with Rosberg — it also pits Mercedes against a fiercely proud Ferrari team chasing its first drivers' title since 2007 and its first constructors' since 2008.
Ferrari is desperate to end its barren run and is banking on Vettel to deliver. The German driver is under enormous pressure. "The sport needs the rivalry and what we've seen has the ingredient of a great championship," Wolff said. "At a certain stage, the best ones that compete for world championships can't be friends. Maybe we've seen the limitation of that respect."
Although Vettel appeared to be more to blame on Sunday, Wolff had some sympathy for him.
"They're warriors and you're at war at that moment, fighting for the race win and the championship," Wolff said. "Emotions are running high."
Hamilton finished fifth in Sunday's race, while Vettel was fourth. Although that meant Hamilton lost a bit of ground, he saw something to exploit over the remaining 12 races, something he considers Vettel's vulnerability under high pressure. "As a team we can only look at that as a positive for us," the Briton said. "He's obviously under pressure and that's not a bad thing if that's how he reacts."
Up next is the Austrian GP in two weeks, Round 9 of their heavyweight contest.