Wolff had clearly stirred things up with Horner over the Montreal weekend when he questioned how Verstappen behaved outside of the car in his approach and attitude.

The Mercedes motorsport boss pointed this out when he told local media that Williams development driver Lance Stroll showed levels of maturity that were greater than Verstappen.

Wolff said: "Max Verstappen acts more like a teenager. In the car, he's extremely good, but when you interact with him, he's a kid. But with Lance, his maturity is very surprising."

Horner hit back at Wolff's comments, though, and claimed that the way Verstappen superbly held off Mercedes' experience Nico Rosberg put a lie to any suggestion he was not grown up enough.

"I think he [Verstappen] has shown great mental strength, to be honest with you," said Horner.

"Monaco was a tough weekend for him, but the way he has bounced back here, the confidence he has had, throwing the car around, was great.

"It hasn't affected him at all. It was a pretty mature drive for somebody that Mr. Wolff said was not quite as mature as he thought.

"He looked pretty mature to me when he was fending off his [Wolff's] very experienced mature driver."