Just four weeks after Hamilton and Rosberg wiped one another out in the Spanish Grand Prix, a Turn 1 skirmish on the opening lap in Canada compromised the championship leader's race.

Rosberg was forced to take to the runoff area after bumping wheels with Hamilton, returning to the track ninth and only finishing fifth behind his race-winning team-mate.

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Horner, involved in his fair share of team orders debates at Red Bull when Sebastian Vettel and Mark Webber, in particular, were battling it out on track, applauded Mercedes for the stance it has taken.

"To me it looked hard racing," said Horner when asked for his assessment of the latest Hamilton/Rosberg coming together.

"It didn't look anything untoward. It's two guys going for a world championship that aren't going to give an inch. Good stuff.

"I doubt they are thinking they are team-mates - they are each other's biggest rival, so they are both going for the same bit of Tarmac.

"The unfortunate thing is they got in the way of Daniel [Ricciardo] on the exit of that turn and he did very well to avoid collecting Nico."

Horner has insisted he would adopt the same attitude if in Mercedes motorsport boss Toto Wolff's shoes, adding: "They are two guys competing for the big trophy. They are racing.

"Unless you condemn one of them to be a number two driver you've got to let them race."

Red Bull did issue its own team order early in the Montreal race when it appeared Ricciardo was quicker than team-mate Max Verstappen, who was instructed at one point not to hold up the Australian.

No change of position occurred, which Horner insisted was "fine".

He explained: "At that point in the race it looked like perhaps Max was having a few more tyre issues than Daniel, and Daniel looked like he had a bit more pace.

"Then the virtual safety car came out and he [Verstappen] pulled away from the DRS, so no reason to interfere."

Asked as to how much time a driver is allowed before complying with such a request, Horner replied: "They've got to be on top of each other so we gave him an early warning.

"Then the virtual safety car came out and he pulled away so it negated that. We monitor it pretty closely."

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