Only Graham Hill has managed the feat and that was completed in 1972, almost 50 years ago.

So what will he do now? Will his focus be entirely on completing his quest and could that mean calling time on his F1 career?

The Spaniard, who will turn 37 next month, picked up his first international race win since May 2013 at the World Endurance Championship race in Spa this season. He backed it up with the Le Mans win on Sunday, partnered with Sebastien Buemi and Kazuki Nakajima.

Overall podium: winners Kazuki Nakajima, Fernando Alonso, Toyota Gazoo Racing Photo by: Nikolaz Godet

He celebrated 300 Grands Prix in Canada but is approaching 100 Grands Prix without a win. With little prospect of a race win in F1 on the horizon, as McLaren lag well behind the other Renault-powered cars – let alone the Ferrari and Mercedes works teams – will he quit F1 to focus on the Indy 500 in May 2019, or will he seek to combine the event with an F1 schedule as in 2018?

The 2019 race calendars have not been set, but in Monaco the promoters of the leading FIA championships met to look at scheduling for 2019. IndyCar was not part of that meeting, but clearly this potential clash will be one that F1 will be keen to avoid.

The World Endurance Championship changed its schedule at Fuji later this year to accommodate Alonso who is doing the WEC championship as well as F1. Alonso is committed to the 'superseason' which takes in two Le Mans 24 Hours and features races next March at Sebring and Spa in May.

Nigel Mansell Photo by: IndyCar Series

Nigel Mansell quit F1 for IndyCar in 1993 and won the championship first time out, including wins on long and short ovals. It would be tricky for Alonso to fit in with IndyCar's schedule, less so if he were just doing WEC and not F1.

This year the IndyCar schedule featured one short oval race at Phoenix prior to the month of May at Indianapolis. None of the 2018 IndyCar races clashed with the upcoming WEC dates, and Sebring would follow on a week after the IndyCar season opener in St Petersburg, also in Florida, which is likely to take place on March 10.

Fernando Alonso, Andretti Autosport Honda, battles with Alexander Rossi, Herta - Andretti Autosport Honda Photo by: Scott R LePage / LAT Images

Alonso is sure to go for an Indy 500 win with all guns blazing now, and it will be interesting to see whether McLaren is the team to enter him – and with which team it would partner, most likely Andretti Autosport.

Last time he ran with Honda engines, but since he split with the marque at the end of last season, the irony of winning Le Mans with Toyota will not be lost on Honda senior management. It is a considerable coup for Toyota, who picked up its first Le Mans win after many years of trying.

Winners #8 Toyota Gazoo Racing Toyota TS050: Sébastien Buemi, Kazuki Nakajima, Fernando Alonso Photo by: Scott R LePage / LAT Images

An historic victory

Alonso won the race in Toyota #8 car, beating the #7 sister car in the process. The Spaniard played his part with an exceptional night-time stint. He dragged the car – which had been over two minutes down on the other Toyota – back onto its tail with a quadruple stint in the night.

After the #8 car took the lead, its advantage grew substantially thanks to a strong stint by Sebastien Buemi and errors from two of the #7 car's drivers. Kamui Kobayashi accidentally extended a fuel stint by a lap, obliging him to drastically reduce speed to ensure he could get back to the pit. Compounding that car's deficit, one of Kobayashi's co-drivers, multiple World Touring Car champion Jose Maria Lopez, spun the car, losing a good 15sec.

Although critics will argue that this was an ‘easy’ win, with both Audi and Porsche withdrawing from WEC and Le Mans in the last two seasons, Alonso (and history) will not care about that. It is another debut win for an F1 driver, following Nico Hulkenberg's 2015 victory with Porsche.

Winners #8 Toyota Gazoo Racing Toyota TS050: Sébastien Buemi, Kazuki Nakajima, Fernando Alonso Photo by: Sam Bloxham / LAT Images

“Alonso has come and conquered Le Mans, along with his team-mates, and not put one foot wrong as we've seen all through the race,” said nine-times Le Mans winner Tom Kristensen.

“I think he also sees the chance to be world [endurance] champion, which means he will continue to drive until Le Mans next year – and I think he will do that.

“I would not predict that he stops in F1, but he'll definitely be back at the Indy 500. Maybe he'll do a full season.”