Sergio Perez overcame rain, red flags and tyre troubles to take a thrilling victory at the Monaco Grand Prix.
But home favourite Charles Leclerc was left frustrated by a Ferrari strategy decision that took him from a comfortable lead early on to fourth.
Perez led home Carlos Sainz and Max Verstappen to become Mexico's most successful driver, surpassing Pedro Rodriguez with his third career victory on a day of chaos and tension.
Heavy rain fell 10 minutes before the race was due to begin, leading to an hour and five minutes of confusion as the FIA first delayed the start for safety reasons, given an ominous radar warning before a deluge ensured a red flag was thrown after one lap behind the safety car.
After the delay, Leclerc charged into an early lead when the race finally got underway with rain forecasted for a return.
But 17 laps into the race and on a drying track, Perez pitted for intermediates and triggered the strategic merry-go-round at the top of the order.
Sainz was called into the pits in response but the Spaniard pleaded with his team to stay on his extreme wet tyres until the switch to slicks was possible, with Ferrari granting his wish.
But the Scuderia pitted Leclerc as Verstappen was brought in for intermediate tyres, giving up track position and when the time to pit for slicks on lap 22, the Monégasque returned to the pits only fourth, leading to an expletive-laden rant on team radio.
Perez went a lap longer on intermediates than Sainz did on the extreme wets, with the warmer tyre temperatures paying dividends for the Mexican, who emerged in the lead.
Following a red flag period for barrier repairs, after Mick Schumacher crashed out, Red Bull opted for mediums whilst Ferrari chose used hards, with Perez keeping Sainz at an arms distance.
But as the race turned into a timed event and with 13 minutes to go, graining began to appear on Perez's medium tyres, giving Sainz a sniff of a maiden victory.
Perez struggled for grip throughout the final 10 minutes with Sainz closing to within millimetres on multiple occasions as Verstappen and Leclerc also closed up.
Traffic was the final obstacle for Perez to overcome, but he held on to clinch the most prestigious victory on the calendar.
Schumacher splits Haas in half in big crash
Schumacher had been one of the risk-takers throughout the opening 25 laps, making an early switch to intermediates before jumping to hard tyres swiftly.
But on lap 26, the German lost the rear of his Haas at La Piscine, spinning into the Tecpro barriers and ripping the rear wheels and wing off the main chassis in a dramatic incident.
It is the second car-splitting accident Schumacher has had this season after his qualifying crash in Saudi Arabia, with strain no doubt being added to his team financially given the overhanging budget cap.
Most importantly, Schumacher emerged from the cockpit under his own power - although was taken for a medical check-up - with the race first neutralised by the safety car and then red-flagged on lap 30 in order for barrier repairs to take place.
Ferrari strategy leaves Leclerc irate
Leclerc's frustration was clear on team radio and even clearer when stood shaking his head in the Ferrari garage during the red flag delay following Schumacher's crash.
The Scuderia not only pitted Leclerc onto intermediates to give up position to Sainz but also gave a muddled call for their driver to box for slicks.
Only after Leclerc had entered the pits did race engineer Xavier Marcos Padros frantically demand "stay out, stay out".
This meant that whilst Sainz was being serviced, Leclerc was momentarily double-stacked and waiting in the pit lane, the lost time costing him track position - and a podium position - to Verstappen.
The decision to pit both drivers before the Red Bulls cost Sainz dearly, with his slow out-lap on cold slick tyres allowing Perez to blast around on warm intermediates and take over the lead when pitting a lap later.
Russell best of the rest as Alonso holds off Hamilton
Yet again, George Russell was the driver to beat behind the Red Bulls and Ferraris, continuing his streak of finishing in the top five at every race this season.
Lando Norris finished a lonely sixth despite continuing his battle against illness, ahead of Fernando Alonso in the Alpine.
The Spaniard was the cork in the bottle in the closing stages, creating a long train of drivers as he managed his tyres.
Lewis Hamilton was powerless to get past the Alpine, whilst Esteban Ocon was demoted from ninth after being penalised for contact with the Mercedes driver.
That left Valtteri Bottas in ninth for Alfa Romeo and Sebastian Vettel rounding out the points finishers.
Gasly puts on Monaco show
An hour and five minutes after the race was originally slated to start, the safety car led the cars out of the pits.
Lance Stroll glanced the barrier at Massenet and picked up a puncture and Nicholas Latifi lost a front wing at the hairpin on the first lap out of the pits, before the safety car peeled off at the end of lap two.
Pierre Gasly pitted with the safety car to switch to intermediate tyres in a gamble from the back of the pack.
The Frenchman started to set the fastest times lap by lap and then provided a collector's item on lap 12 when making an overtake on Guanyu Zhou at Mirabeau, scything down the inside on the faster intermediate rubber.
Another came into La Piscine on Daniel Ricciardo as the McLaren struggled for grip on his ageing extreme wets.
Despite not ending in the points, Gasly's bravery ensured we were treated to a show on the streets of the Principality.
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