Ross Brawn says that exceptional circumstances forced Formula 1 to schedule a 'triple header' for teams in 2018.

Next year's calendar will include 21 races, three of which - France, Austria and Britain - will be held on consecutive weekends.

But F1's sporting boss has made clear that the heavy schedule, and subsequent burden on the teams, was dictated by uncommon events outside of Formula 1, insisting the 'triple header' is an exception and shall never become the norm.

"The (football) world cup presented us with a very unusual problem," Brawn told Sky Germany.

"The final is in the afternoon and it would have been very unfair to have run a race on that weekend," he added.

"We could only solve that by having three races in a row but it's not something we want to repeat in the future. It was an emergency measure," Brawn said.

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