The Spaniard is revered as a master of his metier, but his reservoir of patience with an underperforming car has finally hit empty.
The only surprise about Tuesday’s announcement that he was moving on to Indycar from 2019 was that it had not come sooner.
Since his return to ailing McLaren he has displayed great stoicism and humour as the famous British team struggles to produce a car to match the might of Mercedes, Ferrari or Red Bull.
The 37-year-old, the first Spanish driver to be crowned world champion, has long nurtured a dream to emulate the late Graham Hill and land motorsport’s coveted Triple Crown.
And his move to IndyCar in 2019 may well see him realise the ambition.
He has two legs in the bag, the Monaco Grand Prix and this year’s 24 Hours of Le Mans. That leaves the fabled Indy500 — he led the field on his debut in 2017 before his engine blew.
Born in Oviedo, in the Asturias province of northern Spain, Fernando Alonso Diaz inherited his passion for driving fast cars from his father.
Jose Luis was an amateur kart racer and presented his son with a replica pedal F1 car.
His parents said Alonso showed a competitive spirit at a young age and, like F1 legend Michael Schumacher before him, Alonso embarked on a karting career.
He won three Spanish karting titles before winning the world juniors in 1996.
He eventually graduated to Formula 3000 where he attracted the attention of the Formula One talent-spotters.
Flavio Briatore, the flamboyant Italian playboy became Alonso’s personal manager and guided his career, eventually bringing him to Renault where he claimed the world title for the first time in 2005, at 24 the then-youngest ever champion.
He defended his title the following season, calling on a combination of natural speed and competitive instincts, allied with supreme race-craft and an iron will to win, that invited comparisons with Schumacher.
In 2007 he switched to McLaren, but it proved a fractious time alongside a rookie named Lewis Hamilton.
He jumped stables back to Renault for 2008 and 2009, before Ferrari came calling where he followed in the footsteps of late aristocratic compatriot Alfonso de Portago, who raced for them in the 1950s.
He finished second in the world championship three times for the Italian marque, before rejoining McLaren in 2015.
Whilst leaving the door open for a possible return to F1, Alonso gave every indication in an emotion-charged message on Instagram, that he was bidding F1 goodbye for good.
Written as if to a lover he said: “You were not expecting me and I was not sure if I want to know you.
“When I barely knew how to walk, I ran straight towards the noise, the circuits, without knowing anything about you.
“We had very good times, some unforgettable, others really bad. We have played together against incredible rivals. You played with me and I learned how to play with you too.
“I have seen you changing, sometimes for good and sometimes for – in my opinion – bad.
“I know you love me but be sure, I love you too.”
The winner of 32 Grands Prix typically has promised to see out the 2018 season with “more commitment and passion than ever”.
F1’s loss is Indy’s gain.