Up until the last four laps of the Russian Grand Prix weekend, Lando Norris had done everything right. He took his first pole position in Saturday's qualifying session, ironically in conditions that mirrored the transition from dry to wet at the end of the race on Sunday, pulled off the perfect dry-weather tyre strategy in the first 49 laps of the race at Sochi and, it seemed, had just about enough performance to hold off Lewis Hamilton's faster Mercedes until the chequered flag.
But as his first Formula One win started to come into view, a storm was brewing to the south of the circuit. Dark clouds were rolling in off the Black Sea and the ships on the horizon were soon lost behind a curtain of rain.
Ultimately, of course, the rain hit. Norris was left skittering around on slick tyres after the majority of the field had made the switch to wet-weather intermediates, and he dropped from the lead of the race to eighth before making up a single place to finish seventh.
It's easy to point the finger. A stronger radio call from the McLaren pit wall would have resulted in a race win as, perhaps, would a calmer head in the cockpit. But those judgements are laden with the benefit of hindsight and, had the rain eased off in the final four laps, Norris would have been heralded as a genius.
Yet McLaren was clear on Sunday night: lessons must be learned. As such, what follows is a deep analysis of the final eight laps of the Russian Grand Prix: the mistakes made, the opportunities missed and reason a seven-time world champion with an equally successful Mercedes team calling the shots from the pit wall came out on top.
Norris leads Hamilton by 1.345s at the start of the lap
As Norris crossed the line with eight laps remaining, umbrellas started going up in the grandstands. The first drops of rain were rolling in from the coast, and Turn 5, the most southerly corner on the circuit, was starting to get damp.
Norris was made aware of the umbrellas by his race engineer, Will Joseph, and replied over team radio, "it's spitting quite a bit" as he came through Turn 5.
Norris noted more rain through the middle sector, to which Joseph replied "OK, understood".
Norris leads Hamilton by 1.167s at the start of the lap
After chipping away at Norris' lead lap after lap, Hamilton was just over a second off the lead McLaren as they started lap 47. Within the next few laps he would aim to get within a second, meaning he would be able to attack with the help of the Drag Reduction System (DRS) overtaking aid on the pit straight.
The rain was still light, but the loss of grip between Turn 5 and Turn 10 meant Norris went 3.6s slower than he did on the lap before. It was still unclear from the rain radar if the track would become fully soaked before the end of the race, and the McLaren team was hopeful a second, heavier weather front wouldn't follow the existing one that was starting to pass by the circuit.
"Okay Lando, this intensity [of rain] will stay until the end of the race, we think," Joseph said.
But as Norris exited Turn 4 with a bit of wheelspin, Hamilton visibly closed the gap and started to fill the McLaren's mirrors heading to Turn 5.
"Possibly wet from here until Turn 10," Joseph said as Norris caught a slide that sent him wide and off the track.
Hamilton sensed an opportunity and almost got alongside Norris on the exit of the corner, but with more to lose in terms of his title battle with Max Verstappen than to gain by taking the lead at that particular moment, he thought twice about attempting an overtake.
Norris then pulled a bit of a gap over Hamilton through the middle sector, and on the back straight Joseph informed him "no more LICO needed", which appears to be an instruction for Norris to stop fuel saving by LIfting and COasting at the end of each straight.
It's clear that McLaren was keen to give Norris every opportunity to hold off Hamilton and had saved fuel in preparation for a wheel-to-wheel fight at the end of the race.
Norris leads Hamilton by 0.0996s at the start of the lap
Initially, Norris was dealing with the slippery track surface well and started to extend his lead over Hamilton in the opening few corners of lap 48. If the earlier radio message about the intensity of the rain staying the same held true, Norris still looked in good shape for the victory with Hamilton struggling just as much as he was for grip.
But the Mercedes pit wall was already thinking about intermediates and, as the chasing car, was perhaps more willing to react to the weather and order Hamilton to pit. Hamilton's engineer, Peter Bonnington, opened the radio and calmly told his driver: "Rain intensity is increasing. It's wet at the far end of the circuit".
At the same time, Mercedes had already decided to pit Hamilton's teammate, Valtteri Bottas, to make an early switch to intermediates. Bottas was having a shocking race up to that point and was running in 14th place with nothing to lose when the pit call came through.
From Mercedes' perspective, not only was it worth gambling with Bottas' strategy, but the Finn's pace could also be used a barometer for how the intermediate tyres were performing in the changing track conditions. Bottas came in at the end of his lap 47, by which point the leaders were already halfway round the track on lap 48.
"The key to it was how you were interpreting the weather forecast, because all the teams have got the same rain radar," Mercedes chief trackside engineer Andrew Shovlin said after the race. "We could see the rain coming in, we could see that it was going to start light and what we could see was that it was then going to get heavier, and that was really the thing we were reacting to.
"But in some ways, our decision making was helped by the fact that Valtteri was out of the points and had nothing to lose and we were the first to make the jump. Certainly not leading the race makes it a bit easier to take those decisions."
Hamilton was informed Bottas had pitted midway round the lap, and was told by Bonnington: "We are ready in the box if you need it."
The tone of the message was still very much in the dialogue phase and not an order. Hamilton responded: "It's pretty slippery but it's not raining much."
Meanwhile, Joseph could also see the conditions worsening and was keen to coach his driver round the track.
"Careful through Turn 5," he said. Followed by, "yellow flags at Turn 7".
Norris, who remained silent at this time, sailed wide at the apex of Turn 7 and went into the run off. Fortunately for him, it made little difference as Hamilton was also struggling for grip despite keeping his car between the lines.
Norris then came up to lap Yuki Tsunoda's AlphaTauri, and for the first time a sense of urgency came across in a radio message.
"I need blue flags!" he said, referring to the flags shown to a car when it is about to be lapped and needs to move out of the way.
Once past Tsunoda, Norris was told DRS had been disabled by race control due to the slippery track surface -- another indication that the weather was about to get worse.
Meanwhile, Mercedes could see that Bottas had found a big lap time benefit on the intermediates and was also becoming convinced that a second band of rain would hit the track in the next 30 seconds. If anything, the rain had eased up in the final sector of the lap where Norris and Hamilton were at that time, but the pit wall was convinced it wouldn't last as more and more drivers started struggling to keep their cars on the track.
"Box, box. Box, box for inters," Bonnington told Hamilton.
But Hamilton, who could only judge his progress by the distance to the McLaren in front and the fact he had fewer drops of rain on his visor, ignored the call and stayed out on track.
Talking after the race, Hamilton said: "Lando went off the track in Turn 7 on one lap and I was like 'OK, OK, stay out, it's most likely going to happen again, I'll try to catch him out'.
"Then they called me in and I was like: 'Yeah, but he's right there!'"
Norris leads Hamilton by 2.087s at the start of the lap
As Norris crossed the line to start another lap, he sounded stressed over the team radio.
"How many laps to go?" he asked.
"Four to go," replied Joseph, before correcting himself: "Four after this one, four after this one. Some cars are pitting for inters. Bottas has gone already."
At this point, both the rain radar and the sector times of those on intermediate tyres were starting to merge towards the same conclusion. The middle sector of Bottas' out lap from the pits on intermediate tyres was 5.3s faster than Norris' middle sector on the same lap and he gained another 1.5s in the drier final sector.
If the weather continued to roll in from the Black Sea, there was little doubt that intermediates would soon start to offer a significant lap time advantage. The messages to Hamilton started to move from the dialogue phase to demands.
"So this is the crossover time," Bonnington told Hamilton as he coaxed his Mercedes through the long, sweeping Turn 3. "We have cars going off track."
Red Bull had also seen the way the race was going and pitted Verstappen, who made up two places in the final sector of his in-lap alone as Daniel Ricciardo and Carlos Sainz spun off the road in front of him on the way to the pits. This was a key moment for Mercedes too, because as much as the team wanted to win the race, it knew Hamilton's main goal in the championship was to finish ahead of Verstappen, so the only logical step for Hamilton now would be to follow his title rival into the pits the next time round.
As more cars started to fall off the track in front of the leaders, McLaren didn't appear to be aware of Mercedes' thinking. Norris was about to enter the treacherous Turn 5 and, once again, the main concern seemed to be ensuring he knew what was coming in terms of track conditions.
"Track very slippery from here to Turn 10," Joseph told Norris. "Lots of cars going off."
Over the previous few radio messages it was clear the stress levels were building in the cockpit of the McLaren and at this point they final spilled over.
"Yeah, shut up!" came the reply from the 21-year-old.
Despite Norris' dismissive response, Joseph wanted to keep a potential pit stop in the conversation. McLaren was very aware the weather could turn this race on its head and, even though the team didn't issue an order, it knew a pit stop at this stage might be crucial.
"Lando, what do you think about inter? What do you think about inter?" Joseph asked as Norris headed down towards Turn 13.
"NO!" Norris yelled in response as he came up behind the lapped cars of Antonio Giovinazzi on slicks and Nikita Mazepin, who has already switched to intermediates.
"I need blue flags, what are they doing?" Norris followed up, with no further conversation about whether to pit at the end of the lap.
The conversation on Mercedes' team radio sounded more relaxed, even though the team was now desperate for its driver to pit. Hamilton still seemed content with remaining on track, but Mercedes was also keeping one eye on the championship and what Verstappen was doing.
"Verstappen has pitted for inters," Bonnington told Hamilton on the approach to Turn 13. "It looks like Norris might do as well. We have a free gap, so box, box. Box, box."
But as Hamilton negotiated Turn 14, 15 and 16 he was still having doubts.
"It's stopped raining, man," he replief.
At this point Mercedes head strategist James Vowles was about to intervene. He had his finger hovering over the button to open comms to his driver and lay down the law. Under Mercedes' pit wall protocol, whatever Vowles says goes -- regardless of what the drivers might think.
But just as Vowles was about to open his radio communication to the car, Hamilton hit the pit confirm button on his steering wheel, signalling that he intended to enters the pits and switch to intermediate tyres.
"The key point that we were thinking to get across to him is that Max had stopped, and with Max having stopped it was certainly key that we shadow what he was doing even if it meant that we might leave the door open for Lando to take a win," Shovlin explained after the race.
"The other thing that we had to get across was that we thought the rain was going to get heavier and therefore jumping early was going to be better. With all these things, it's very much a case of getting the right information to the driver because we were very clear on what we wanted to do.
"The drivers don't have the luxury of rain radars and things, so it's just a case of making sure that they can understand why it is that we are trying to make that decision."
Norris leads Hamilton by 18.464s as Hamilton exits the pits
As Hamilton pitted behind him, Norris' only hope for victory was that the rain eased off and the track started to dry -- or least stopped getting wet. Bottas' previous lap was just over three seconds faster than Norris', so there was a chance that if Hamilton was limited to a similar lap time for the rest of the race, Norris could still hold on for the win.
"Okay, Hamilton has taken it -- he's gone to an inter," Joseph informed Norris.
"Yes I see, I see," Norris replied. "We just need to commit to slicks"
Lap 50 was the trickiest lap yet for Norris. He passed Mazepin (who was already on intermediate tyres) on the entry to Turn 5 but had zero traction on the exit and the Haas, which is the slowest car on the grid in normal conditions, sailed back past.
But at that stage of the race the first and final sectors of the lap were still looking relatively dry, and Norris re-passed Mazepin through Turn 15 and Turn 16. The prudent choice to ensure a podium finish was still to switch to the intermediate tyres at the end of lap 50, but with Hamilton closing the gap to Norris by four seconds on his out-lap alone, a pit stop at that stage would have conceded the lead to Mercedes.
McLaren and Norris were all-in at that stage on the slick-tyre gamble, and it had become a case of 'win or go bust'.
"Okay Lando, just to confirm, we have to be able to stay on track here," Joseph told Norris towards the end of the lap. "You have to stay on this tyre."
Norris leads Hamilton by 14.995s at the start of the lap
As Norris started lap 51, things did not look good. The heavier band of rain had well and truly hit Turn 5, and even Turn 3 was getting wet, with the McLaren driver at less than half-throttle as he tip-toed through the corner. But the worst was yet to come. As he exited Turn 4, Norris was met by a wall of spray and a fully wet track.
"It's f------ ... it's so wet boys!" he said over team radio. "I've got to box. I want to swap, I can't do this!"
Norris' car then slithered wide on the entry to Turn 5, spun through 180 degrees and came to a halt in the run off. He kept the engine running, but as he got going again, Hamilton swooped past and took the lead.
On the back straight, Norris was still struggling to keep the car in a straight line with wheelspin in fourth gear. He only just reached fifth gear before needing to brake on a section of track where the cars would usually have the throttle wide open in eighth gear.
He managed to get back to the pits, but with no grip from his slick tyres ran wide on the pit entry and crossed the white line between the pit lane and the race track. As he did so, Verstappen passed him to take second place.
The Red Bull driver had started the lap 73 seconds behind Norris, underlining just how much time was lost for McLaren as the worst of the weather came in.
Lap 52 and 53
Norris finishes the race 87.224s behind Hamilton
Norris rejoined the race on lap 52 battling with Kimi Raikkonen for seventh position -- a fight he managed to win on the last lap. He then returned to the pits at the end of the race, turned off the car and sat motionless for a minute or two with his head resting against the cockpit protection.
Just four laps earlier he could almost taste the champagne of his first F1 victory, but in that moment he was leaving Russia without so much as a trophy for his efforts.
What did McLaren say after?
With the benefit of hindsight, McLaren's mistakes are clear. Perhaps the biggest one came on lap 49 when the team should have been aware that Hamilton would have to pit to cover title rival Verstappen and pitted Norris from the lead. On that lap, McLaren raised the possibility of pitting, but at no point did it order Norris to do so.
Norris was clearly feeling the pressure at that point of the race, with two terse responses to Joseph's attempts to start the dialogue, and in his mind wholeheartedly believed that the slick was the better tyre to be on. McLaren's pit wall had the benefit of information from the rain radar as well as the lap times of other drivers who had already pitted, but demanding a driver to pit from the lead of a race when he clearly doesn't want to, and may not even need to, is never an easy decision.
"As always in these tricky situations, it is about the communication between the driver and the pit wall using all the information we have available in terms of weather forecast, what the other cars are doing and trying to brief Lando, but at the same time get the feedback on how the track conditions are," McLaren team principal Andreas Seidl said after the race.
"That is how we had to make a decision on what to do and whether to pit or not. With all the information he had from us and how he felt the conditions were on the track, he felt good on the slick tyres and in the end we didn't overrule him as a team. That's something we need to look into because with hindsight it was, of course, the wrong decision that we made as a team.
"But we win together and lose together. The important thing is to learn from it and move on. I think we have seen a lot of positives this weekend and Lando has done a sensational job all weekend.
"He did a sensational job in the race and unfortunately didn't end up with the result he deserved at the end of such a weekend. Up to the last three laps it was actually a pretty good weekend for us."
And Seidl admitted the pit wall itself was not 100 percent sure on what the right move was on lap 49.
"If we would have been crystal clear from the team side and 100 percent convinced it was the right decision to stop, then we would have stopped," Seidl said. "So in the end it was a close call and, of course afterwards it's easy to say it was the wrong call.
"But I think it was quite close to saying what was the right thing and that's why I say in the end it is a team decision together with Lando. The only thing we need to analyse is that if there was any information available it should have led us to make a clear call."
Perhaps McLaren's silver lining was that its car was able to race for the win in the first place. The team won as recently as the Italian Grand Prix two weeks before, but prior to that it had not won a race since 2012, so progress is clearly being made.
It might not seem like much consolation right now, but lessons like the one in Russia will improve the racecraft of both team and driver as they look set to become more competitive in the coming years.
On Sunday, the more experienced and better equipped combination of Hamilton and Mercedes won the race, but McLaren can take a lot of pride from making it incredibly tough for them right up until the final three laps.