It took just three days for McLaren and Honda to discuss, plan and confirm a deal that would see Fernando Alonso make his Indianapolis 500 debut next month... and even then it was borne out of a 'joke' in the first place.

Two-time F1 champion Alonso shocked the motorsport world by announcing he will skip the Monaco Grand Prix with McLaren-Honda in favour of driving a Honda-powered, McLaren supported Andretti Autosport IndyCar in the 101st running of the iconic Indy 500 next month.

With Alonso emphasising his desire to chase the coveted 'Triple Crown' - winning the Monaco Grand Prix, the Le Mans 24 Hours and the Indy 500 - as his primary motivation to change tact in his racing career, new McLaren CEO Zak Brown has revealed it was an off-hand comment during the Australian Grand Prix that ultimately raised the possibility of a bid.

However, it was only during the Chinese Grand Prix weekend that McLaren and specifically Honda got the ball rolling on plans, with a formal announcement made just days later ahead of this weekend's Bahrain Grand Prix, much to the sport's surprise.

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"I had aspirations for us to get back to Indianapolis in the future and the thought of doing it with Fernando Alonso and Honda was a stunning idea, felt a bit like a dream and probably a bit early to start pursuing it," admitted Brown during an arrange press conference in Bahrain.

"It is one of those where it's one of those jokes with some truth to it. So I said to Fernando before Australia 'one of these days we should do Indy together'... just kind of threw it out there to see what kind of reaction I would get it, and he kind of joked back. I thought 'Ok, I'm throwing the bait out in the water but I'll leave it at that'.

"Then in Australia it came up in conversation, one of the mornings, and Fernando brought it up and said 'Honda, you have an unbelievably great history at the speedway, I have a dream to win the Triple Crown and want to do Le Mans in the past and I'd love to do the Indy 500 with you.

"There wasn't a timeline on it but I thought 'Ah, he might actually be serious about this!' Fernando and I speak on a regular basis and shortly thereafter, a couple days, I said to Fernando... I just wanted to say 'we ought to do this Indy thing', but he said 'no, no, no, I want to do dinner in China, and this is what I want to talk to you about'. So then I thought he's really serious about this!"
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"So ultimately at our dinner in China we discussed the ways we could go about doing it, discussed it with Honda, had dinner with myself, Eric, Fernando, his manager Luis, and he said 'I'm going to go sleep on it'. Woke up the next morning and Fernando said 'Let's go do the Indy 500 with Honda'. [I thought] 'Oh man, now I've gotta pull this off!' And we did! I think we're all very excited about it."

For Alonso, whilst he was always committed to the idea of racing in the Indy 500, he admits he had no idea it could come together so quickly, just 46 days before the race.

"Two days ago, it became serious. In Australia, we had a general talk about the future, future of McLaren as a team, as a group, me as a racer, what were the ambitions, the Triple Crown, and McLaren's ambitions in terms of the future to expand from Formula 1, so we talked about these.

"Eric is French, so he was very keen of 24 hours of Le Mans in the future for McLaren, Zak is American so he was very keen of Indy 500. I was in the middle so it's like having two girlfriends and having to like both of them, so I was saying to Zak that the Indy 500 was a great idea for the future, I would say to Eric that 24 hours of Le Mans was a great idea for the future!

"Then after Australia I was in Los Angeles for the shooting and I received a call from Zak about different things, not this one, and in one moment of the conversation it came out again the Indy 500 possibility, and at that point I was happy that McLaren was considering this Indy 500 entrance as they've won in the past a couple of times and this was a different idea that Zak was bringing to the team so I said well, this is kind of interesting for the future and I'm happy when Zak joined the team last year but I was even happier when Zak was telling me these plans about the future.

"In a way I was thinking for 2018 as a possibility because obviously it was 55 days away of the 2017 Indy 500 so in China we had a dinner together and we talked a little bit more serious about this, and we decided this is going to happen, has to be may be like tomorrow the decision, so I said I will sleep tonight, on Friday, and then on Saturday I'll tell you.

"On Saturday I arrived to the circuit and I said yeah, that will be a great idea and a good decision for e
everyone, as I said before a win-win situation for the sport, for McLaren, for myself, for the fans, for everyone, and two days ago on Monday everything became real, which I was not completely sure in Saturday in China if that's still possible, the possibility to make it so quick."

Alonso's Indy 500 bow has been made possible by Stefan Wilson - brother of late former F1 and IndyCar driver Justin Wilson - stepping aside and allowing the Spaniard to assume his entry.