How F1 ended up with a one-car grid and what would have happened if no cars took Hungarian GP restart

It was one of the most unusual sights in modern Formula One history as Lewis Hamilton lined up on an empty grid, waited for the lights to go out and raced himself down to Turn 1.

Such a situation has never happened before and is unlikely to ever happen again, but it could have easily been more even more surreal if no cars had arrived on the start/finish straight to take the restart of Sunday's Hungarian Grand Prix.

So what happened, why didn't Mercedes also pit for slick tyres and what would race control have done if no cars had opted to take the restart?

What happened?

When rain started to fall in the build-up to the Hungarian Grand Prix, it was quite literally the perfect storm. All 20 cars had completed their reconnaissance laps on the way to the grid in dry weather, but after the various prerace ceremonies and rituals in the 30 minutes before the start, the rain started to fall.

The wet track meant all the cars were fitted with intermediate tyres for the start of the race, but after an entirely dry weekend up to that point, the run to Turn 1 was always going to be treacherous. The inevitable happened once the lights went out, with two multiple-car pileups taking out four cars on the spot and leaving a number of others damaged.

The race was first put under a Safety Car and then suspended with a red flag to allow marshals to clear up the wreckage. The remaining 16 cars returned to the pits, where the teams were allowed to work on repairs and, if they wanted, fit different tyres.

Many of the front-runners had been involved in the collisions, with Valtteri Bottas, Sergio Perez and Charles Leclerc all out of the race and Max Verstappen down in 13th place. The big gainers were Esteban Ocon, Sebastian Vettel, Carlos Sainz, Yuki Tsunoda and Nicholas Latifi, who all avoided the carnage and were lined up in that order behind Hamilton, who retained the lead.

The rain eased off during the stoppage and in the heat of the Hungarian summer, the track dried out around the circuit. It would not have been surprising if at least one of the teams had gambled on slicks for the restart (and it could have been a race-winning decision), but they all believed the track was still wet and sent their cars out for a formation lap ahead of the standing restart on intermediate tyres.

As the drivers went round the 4.3km circuit and discovered a dry track, there was a flurry of radio communication and all but Hamilton decided to head back to the pits to fit slick tyres. It was the right choice, but it led to the remarkable sight of Hamilton sitting alone on the grid on intermediate tyres while the other 15 cars all fought for position on the other side of the pit wall to fit slick tyres and join the queue to restart the race from the end of the pit lane.

Why didn't Mercedes pit?

With the benefit of hindsight, Hamilton would almost certainly have won the Hungarian Grand Prix had he pitted with the rest of the field on the formation lap before the restart. By completing one lap on intermediates after the restart and then pitting for slicks, he dropped to the back of the field and faced a long fight back to eventually finish third on the track, which became second when Vettel was disqualified.

Mercedes considered pitting Hamilton but felt the decision came laden with risk. Having seen Hamilton's title rival Verstappen drop down the field on the opening lap and knowing the Red Bull had significant damage, the team believed keeping Hamilton on track was the safer option.

"When we actually left the pit lane [for the formation lap before the restart], we were talking about whether to go on slicks, because we could see that it was drying out, and that's really the decision that we got wrong," Mercedes chief engineer Andrew Shovlin said. "The mindset, though, was, given the situation with the race start and with our competitors, one of not making a mistake by slipping off or getting tangled in an accident.

"So we decided to be cautious and go on the inter. It was very surprising to see the entire field on the inter, and then it was even more surprising to see the entire field peel off behind us."

But it would not have been as straightforward as pitting from the front of the queue and rejoining in first place from the end of the pit lane. Once the teams decided to pit, it was essentially a free-for-all during the tyre changes, with the order of the cars thereafter decided by how quickly the tyres could be changed and the car released back into the queue.

That's why the positions changed significantly during the pit stops, with Latifi emerging in third place, Tsunoda moving ahead of Sainz and Nikita Mazepin dropping out of the race when he collided with Kimi Raikkonen, who was released by his Alfa Romeo pit crew into the Haas driver's path.

What's more, the Mercedes pit box was the first one on the right as the cars enter the pit lane and Hamilton likely would have been blocked in for longer as the cars filed past, dropping him down the order.

"When you are first garage, you've got the disadvantage that as you come in and do your stop, you've got a train of cars following you in, who all have pit boxes further down the pit lane," Shovlin explained. "Then you've got to try and find a gap where you can launch into. You saw that there were a few incidents with people crashing in the pit lane.

"Looking at it, and knowing there's no way Lewis could build a five-second gap on the formation lap because everyone is trying to bunch up and get in, we think we would have been best case P6 on the road, worse case P10. But it would have still been messy and risky.

"That's why we go back to the real mistake that we made, which was we should have rolled out of the pit lane on dry tyres [for the formation lap], as should have everyone. Because then you don't need to make the stop.

"It was unfortunate, and we had an easy opportunity to win the race which we failed to take. But, we were all in agreement that we all got it wrong together. No-one is being blamed for it, and it's one of those things which you learn from and in this industry you try not to make the same mistake twice."

How did George Russell emerge in second, and why did he give the place back?

Such was the chaos in the pits that George Russell emerged in second place despite entering in eighth. He stopped for tyres after his teammate, Latifi, who entered in sixth place and rejoined in third; left the Williams pit box, which is the last one in the pit lane; and simply drove down the side of the queue of cars and past Ocon, who was at the head of the queue. Russell's timing coincided perfectly with the lights at the end of the pit lane turning green, meaning he rocketed out ahead of Ocon, who had already been waiting for some time.

Williams realised the error immediately and told Russell to drop back to eighth place once he was on track. On Sunday evening, race director Michael Masi confirmed he would have referred the incident to the stewards had Russell not slowed to let the other cars past, which would almost certainly have led to a penalty.

"Firstly, thanks to the FIA for showing a little bit of common sense as they could have given me a drive-through, which would have been a bit harsh," Russell said. "It's a unique situation, everyone queueing, I saw an opportunity and thought let's go for it. But glad we were allowed to hand the positions back, a bit of common sense."

What would have happened if no cars were on the grid?

Of course, it was entirely possible that Hamilton also pitted and there were no cars on the grid as the lights went out. Like the one-car grid we saw Sunday, it would have been an unprecedented situation but would have had a fairly simple solution.

"I haven't had one of those before -- it was a bit different," Masi said. "What would have happened [if Lewis had pitted], basically once the last car was in the pit lane, the start signal would have been initiated and then once that went off, the green light at pit exit would have come on and it would have been the order at pit exit."

Masi said the situation would be reviewed in the coming weeks to ensure procedures are in place to deal with a similar eventuality in the future, but also pointed out that the confusion resulted in an interesting outcome.

"It's nothing anyone could have ever foreseen, but we'll let things calm down and have a chat about it in the light of day with all the sporting directors. But having spoken to some of them already up and down, some of them have already said, 'was it really a bad thing?'"