Lewis Hamilton was denied a record-equalling victory at the Russian Grand Prix after he was hit with a 10-second penalty.
Valtteri Bottas took advantage of his Mercedes team-mate's punishment to claim only his second win of the campaign with Red Bull driver Max Verstappen second and Hamilton third.
Hamilton was penalised by the stewards for performing two illegal practice starts ahead of a race in which he had hoped to claim his 91st victory to match Michael Schumacher's all-time tally.
The penalty dropped him out of contention, with the world champion blasting the decision as "bull****."
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With Hamilton out of the way, Bottas marched to a regulation victory, crossing the line 7.7 seconds clear of Verstappen. Bottas reduced the championship lead to Hamilton to 44 points after 10 of 17 rounds.
Hamilton will now also have to toe a disciplinary tightrope after he was dealt two additional points on his licence, taking his 12-month tally to 10.
If he receives two further penalty points at any stage during the next four grands prix, he will be hit with a one-race ban.
After roaring to pole position at the Sochi Autodrom, Hamilton headed into Sunday's race as the favourite to re-write the sport's record book.
But his hopes were up in smoke just moments after he left his garage. Hamilton radioed in with the Mercedes pit wall to see if he could perform a practice start in the pit-lane exit.
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Hamilton was informed by race engineer Pete Bonnington that he could but the decision came back to bite the Brit and his team with the tactic not permitted in the rules.
Hamilton was immediately under investigation, and despite holding off Bottas at the getaway and again at the restart – after the safety car was deployed following two separate crashes involving McLaren's Carlos Sainz and Racing Point's Lance Stroll on the opening lap – he was told he would have to surrender his lead.
"Lewis we have a 10-second penalty," said Bonnington. "What happened? What happened?" Hamilton hastily asked.
"Those starts going to the grid, we got a five-second penalty for each," replied Bonnington.
"That is bull****," said Hamilton. "Where is that in the rulebook?"
Article 36.1 requires drivers "to use constant throttle and constant speed in the pit exit." The stewards deemed that Hamilton was in breach of the rule by "performing his practice start near the end, but directly in the pit exit."
Hamilton served his penalty when he came in for new rubber on lap 16, dropping him to 11th, 36 seconds behind Bottas.
"This is ridiculous, man," he said. Hamilton also hit out at his team for bringing him in too early, and midway through the race when he was informed of the gap to Verstappen, Hamilton snapped: "I don't want any more info, Bono. It doesn't make any difference."
Hamilton moved up the pack as those in front of him stopped for tyres but he was unable to make any impression on Verstappen, finishing 15 seconds behind the Dutchman.
"Not the greatest day, but it is what it is," said Hamilton immediately after the race.
Asked about the penalty, he replied: "It doesn't matter, it is done now. I take the points I have got and we move on."
Hamilton will now have to tread carefully at the rounds in Nurburgring, Imola, Portimao and Istanbul to avoid a one-race ban.
On an otherwise largely uneventful afternoon, Sergio Perez finished fourth for Racing Point ahead of Renault's Daniel Ricciardo and Ferrari driver Charles Leclerc.