Hamilton and Vettel were running first and second ahead of the second safety car restart at Baku when the Ferrari driver ran into the back of the Mercedes.

Vettel felt Hamilton had brake tested him and subsequently pulled alongside the Mercedes before swerving right and making contact.

The stewards gave Vettel a 10-second stop/go penalty for “potentially dangerous” driving with Hamilton saying his title rival “disgraced himself” with his actions.

Horner, Vettel’s former boss at Red Bull, believes the German reacted “in the heat of the moment”.

He said: “Sebastian obviously felt that Lewis brake tested him.

“Then it just looked like a red mist moment to me, where he's lost it and taken a swipe at him, which was only ever going to result in a penalty.

“But, you know, it's heat of the moment stuff and, yeah, a penalty was inevitable after that.”

Vettel ultimately finished fourth, with Hamilton fifth after an extra pitstop to repair a loose headrest dropped him down the field from the lead.

The result means Vettel extended his championship lead to 14 points with 12 races to go.

Horner believes the incident adds to the increasingly intriguing title battle with the two drivers.

“Emotions are running high, they're fighting for a world championship,” said Horner.

“It cements the rivalry between the two of them, for the rest of the season.

“It’s going to be a great championship battle throughout the rest of this year.”

Daniel Ricciardo won the race, giving Red Bull its first win of the season, and Horner hopes the team can be more involved at the sharp end.

“We’re too far out of contention to compete for the championship,” he said.

“But I think we're gaining performance and speed to be able to compete for race wins, as we're getting more and more performance of the car.”