What is the 2027 engine dispute that could dictate Verstappen's future?

At the weekend's Canadian Grand Prix, Max Verstappen renewed his threat that he could quit Formula 1 at the end of this season if the sport's power-unit regulations do not change, but could there be more to the story than simply the Red Bull driver's frustrations?

Verstappen first revealed he was considering his future following the third round of the season in Japan at the end of March, as he was unhappy about the unnatural style of driving and racing caused by the new car rules.