Alonso to skip Monaco to race Indy 500

But the Indy 500 may have looked even more tempting given McLaren are now last in the Formula One constructors' world championship after two races without a point.

McLaren CEO Zak Brown must be barking mad to allow Fernando Alonso to race in the Indianapolis 500, says Red Bull team principal Christian Horner.

"I'm thrilled to be making a one-off return to Formula One racing, and I couldn't think of a better place to make that return than my adopted home Grand Prix of Monaco", Button said in the McLaren statement.

"The possibility to win a big race, a big trophy like the Indy 500 in the middle of a year is like winning a World Championship in one weekend", he said.

However, Alonso insisted Monaco would be the only F1 race he would miss intentionally this season.

Button remains under contract with McLaren after agreeing a two-year ambassadorial role, but he is yet to drive this year's auto. It was rumored former driver Jenson Button would fill the empty McLaren seat for the Monaco GP, and now, we know for sure: Jenson Button will return to Formula One.

"I was truly delighted when Jenson accepted our suggestion that he race at Monaco instead of Fernando", Boullier said.

"I rang him, we just discussed it and his first reaction was 'great, I'm so excited!' It was an easy discussion to be honest, very straightforward".

In truth, the 37-year-old, who is still paid a hefty sum - understood to be in the region of £5 million a year - by McLaren in his role as their ambassador, probably had little choice.

The Briton made clear last November that he was not expecting to return - and it is not clear whether he would be willing to do so now - but he has kept fit competing in triathlons and training in California.

I think, as a team, to be racing in the same day in Monte Carlo and in the Indy 500, two McLaren-Hondas in different series, is an unbelievable thing for motorsport fans.

Alonso's motivation is part of a wider ambition that also includes the Le Mans 24 Hours endurance race.

"We have Stoffel [Vandoorne] who we believe has one of the greatest potentials and will be also there".

Still, while this is being done in the service of chasing that Triple Crown, it'll be extremely tough for Alonso to win the Indy 500 during his first time racing in the event.

Despite the massive challenge Alonso faces of learning to come to grips with an IndyCar and one of the world's fastest racing circuits (he has never driven an IndyCar, or on a superspeedway) in just over a month, the Spaniard is relishing the prospect of rising to the occasion.

"I think us drivers should be able to do more than one series", Hamilton said.