Lewis Hamilton's Italian Grand Prix was undone by a pivotal stop-and-go penalty on a dramatic day at Monza as Pierre Gasly won the first Formula 1® race of his career.
The F1® championship leader had looked on course for another serene afternoon having built up a sizeable lead when he pitted prior to the race's halfway point, only to discover he had erred due to the pitlane being closed following Kevin Magnussen's retirement.
It proved even more costly shortly after, though, as Charles Leclerc's big crash resulted in the race being suspended and the field being bunched up again, meaning Hamilton was last once he had served his penalty upon the resumption.
He could only get back up to finish seventh, and it was AlphaTauri's Gasly who held off McLaren's Carlos Sainz to take an incredible victory, with Racing Point's Lance Stroll third.
Pole-sitter Hamilton pulled away from the starting grid with no problems but it was a different tale for his team-mate Valtteri Bottas, who was caught off the line by Sainz and proceeded to fall back to sixth across the first lap.
Ferrari's nightmare at their home grand prix began when Sebastian Vettel's brakes failed on the sixth lap, though it was the next retirement that would inject the first dose of real drama.
On the 20th lap Haas' Magnussen broke down just before the pitlane, which was subsequently closed, but Hamilton and Antonio Giovinazzi went in for fresh tyres anyway, leading to an FIA investigation.
While that probe went on, Vettel's Ferrari team-mate Leclerc lost control at the Parabolica, smashing into the tyre barrier, which brought out the red flags and resulted in a race stoppage.
Hamilton was out in front at the time of the suspension but soon learned that he, like Giovinazzi, had incurred a 10-second stop-and-go penalty.
Although he fended off Stroll and Gasly when the race resumed from a standing start, Hamilton returned to the back of the pack after serving his penalty.
Gasly, whose pitstop during yellow-flag conditions earlier in the race proved a masterstroke, had Sainz pushing him all the way but held on for a thrilling win by less than a second.
LONG-SHOT GASLY TRIUMPHS
He was considered as long as 2,000-1 to win this race before it started, but Gasly kept his head amid all the madness in Monza.
He started the day 10th on the grid and could have not expected what followed but, resuming in third after the mid-race stoppage, he quickly passed Stroll off the line and was then left out in front as Hamilton pitted for his penalty.
Sainz applied plenty of pressure in the closing stages but Gasly was able to stay in front for a memorable, and popular, victory.
AN UNFAMILIAR TOP THREE
Prior to this Italian Grand Prix, the podium in five of the seven races this year had featured the same three names – Hamilton, Bottas and Max Verstappen.
But on one of the most extraordinary Sundays in F1® history, the big guns were nowhere to be seen when the checkered flag came down.
Between them, Gasly, Sainz and Stroll had previously had just three podium finishes and, in a season of such predictability, their places on the three steps were a very welcome sight.
RARE MERCEDES MISTAKE COSTS HAMILTON
The last time Hamilton finished outside the top four in a race was at the 2019 Brazilian Grand Prix, when he was awarded a post-race penalty for making contact with Alexander Albon to drop from third to seventh.
Here, the punishment came within the race. Hamilton failed to spot the light on turn 11 informing him he could not enter the pit, though he complained there was no evidence of the closure on the pitlane itself.
If there was a crumb of comfort for Hamilton, it was that his championship rivals all endured frustrating days too and he set the fastest lap to retain his 47-point cushion in the drivers' standings.
IN THE POINTS
- Pierre Gasly (AlphaTauri)
- Carlos Sainz (McLaren) +0.415s
- Lance Stroll (Racing Point) +3.358s
- Lando Norris (McLaren) +6.000s
- Valtteri Bottas (Mercedes) +7.108s
- Daniel Ricciardo (Renault) +8.391s
- Lewis Hamilton (Mercedes) +17.245s
- Esteban Ocon (Renault) +18.691s
- Daniil Kvyat (AlphaTauri) +22.208s
- Sergio Perez (Racing Point) + 23.224s
- Lewis Hamilton (Mercedes) – 164
- Valtteri Bottas (Mercedes) – 117
- Max Verstappen (Red Bull) – 110
- Lance Stroll (Racing Point) – 57
- Lando Norris (McLaren) – 57
- Mercedes – 281
- Red Bull – 158
- McLaren – 98
- Racing Point – 82 (after 15-point deduction)
- Renault – 71
The drivers remain in Italy for next week's Tuscan Grand Prix at Mugello, which will be Ferrari's 1,000th race.