The Spanish Grand Prix provided the fourth consecutive contest which saw Lewis Hamilton and Max Verstappen fight on track for race victory.
For the third time out of those four events, it was Hamilton and Mercedes who emerged victorious, strengthening his championship lead to 14 points in the process.
As has been the case before, Verstappen and his Red Bull team were left wondering if there was anything they could have done differently to beat the reigning world champions.
Mercedes beats Red Bull on strategy
Sunday's Spanish Grand Prix may not have been a classic -- it's rare that a race at the Circuit de Barcelona-Catalunya is -- but another important dimension in the title battle emerged: pit strategy.
Over 66 laps, a chess match played out between the pit walls of the two teams, with Red Bull making an aggressive opening gambit while Mercedes played the long game and forced Verstappen into checkmate on lap 59.
Based on the way the tyre's behaved in Friday practice, the consensus among teams was that it would be a one-stop race, but by remaining open-minded to a two-stop Mercedes kept itself in contention for victory.
First blood went to Red Bull as Verstappen, who started second on the grid, muscled his way past Hamilton at Turn 1 and into the lead.
Track position is vitally important at the Circuit de Barcelona Catalunya and, in theory, Verstappen's lead would allow Red Bull to dictate the pace of the race.
But Hamilton was determined for that not to be the case, and while he wasn't fast enough to retake the position on track, he pushed Verstappen hard to try to expose any weakness on the Red Bull.
Throughout the opening four races, the Mercedes has been the better car at looking after its tyres and if Hamilton could up the pace enough, he had the chance to take advantage of that strength.
It was surprising for both pit walls when Verstappen pitted first on lap 24, taking the decision from the cockpit to trade his soft compound tyres for mediums.
Mercedes had been prevented from pulling the trigger on a pit stop any earlier as Hamilton would have emerged directly behind Verstappen's teammate, Sergio Perez, and likely lost any advantage that came with the early tyre change.
"He called himself in," Red Bull team boss Christian Horner said, referring to Verstappen's decision to pit first. "So we weren't expecting him which is why the pits weren't ready, so that's why the stop was slow. "I think the boys did a phenomenal job to recover so quickly and we lost a bit of time but managed to retain track position so salvaged it very well there."
Verstappen added: "It was just miscommunication between when to pit. I thought I had to pit that lap and clearly it wasn't - but luckily we didn't lose too much time with that."
Verstappen's four-second pit stop (typically teams aim for 1.8s-2.5s) opened the possibility for Hamilton to pit the following lap and take the lead, but the data on the Mercedes pit wall suggested that, even with the delay at Red Bull, it would have been marginal and Hamilton would have probably emerged behind.
Tyre changes have not been a strength of Mercedes so far this season, and there was the potential for a few lost tenths of a second to result in Hamilton resuming in second without taking advantage of the Mercedes' inherent strength of looking after its tyres.
Instead, Mercedes told Hamilton to continue for a further four laps, giving him slightly fresher tyres for the second stint at the cost of a gap of about 5.0s that Verstappen was able to build on the fresher rubber.
However, Red Bull now knew that Verstappen was going to have to nurse his tyres to the end of the race (42 laps in total), and as the Red Bull duly backed off, the 5.0s advantage was quickly whittled away by Hamiton, who was back within a second of Verstappen by lap 33.
Closing on a driver is one thing at the Circuit Barcelona Catalunya, but passing is another. In order to make a successful pass, Mercedes' engineers calculated that the car behind needed a 1.2s advantage over the car in front and Hamilton's four-lap tyre advantage wasn't enough.
Had the race run to the end as a one-stop, the relative wear of the tyres of the two cars would have allowed Verstappen to hold Hamilton off, so the only option was to go aggressive and make the race a two-stop.
Mercedes' pit wall pulled the trigger with its second stop on lap 42, dropping Hamilton to third place behind teammate Valtteri Bottas, but with tyres capable of lapping up to 1.8s faster than Verstappen.
With 24 laps left and a gap of 23 seconds to Verstappen to make up, the maths turned in Hamilton's favour and, in chess terms, Mercedes had Red Bull in check.
Had Verstappen pitted a lap later than Hamilton he would have resumed behind the Mercedes, such was the pace of Hamilton's outlap, but if he stayed out there was a chance that a well-timed Safety Car might grant a free pit stop, allowing him to pit and stay ahead, or simply Hamilton wouldn't find the pace to close the gap.
In theory, Red Bull could have pre-empted Mercedes' second pit stop and pitted Verstappen earlier than Mercedes, but doing so would have sacrificed the lead, dropped Verstappen behind both Mercedes cars and put a huge amount of pressure on Verstappen to fight back.
But Mercedes was still worried given the direction the race was developing.
"When it came to the point when we pulled the trigger, we were nudging to the point where we were worried Max was going to do it before us," Mercedes head of trackside engineering Andrew Shovlin said.
"Looking at the degredation rates and hearing the comments on the radio, we get an idea of wear on the cars' tyres and what we thought was a bit of a long-shot ahead of the race and even in the early stages of the race, we actually thought by that time that it was the right thing to do."
With the benefit of hindsight, it would have given Verstappen his best shot of victory over the final third of the race, but in that moment, when he was leading the race, you would struggle to find a single strategist in F1 brave enough to make the call.
"It'd be a hell of a bold decision to pit from the lead on lap 42 when all the predictions are that the tyres should have -- and they would have -- got to the end of the race," Horner said after the race.
"It would have been the fastest way to the end of the race, but track position is crucial here, and we had been able to maintain track position to Lewis up to that point.
"Also they had a set of mediums available to them, we had a set of softs, we wouldn't have had the range that those mediums had."
On lap 59, Hamilton used his significant tyre advantage to cruise past Verstappen, take the lead and secure his fifth Spanish Grand Prix victory in a row. The overtake won't make the highlights reel at the end of the year, but it was hard earned by Mercedes and would have been as satisfying to the team as any other.
Does Mercedes now have the faster car?
After the race, Verstappen pointed to Hamilton having the faster car and claimed there was nothing his team could have done to win the race.
Yet Mercedes believes it would have looked as weak in the final stages of the race as Verstappen did had Red Bull made the bold call of making a second pit stop first.
Without running the race again, it's hard to determine what would have happened, so close was the performance of the two cars, but its seems as though Mercedes had a slight advantage.
Perhaps that's no surprise given a Mercedes has been on pole at every Spanish Grand Prix since 2013 and won seven of the last eight races.
But this was as close as Red Bull has been at this circuit since 2016 when the two Mercedes drivers took each other out and gifted Verstappen his first F1 victory.
In qualifying, the gap between Hamilton and Verstappen was as little as 0.036s and it was equally small in the race.
Look at the fastest lap attempts of Bottas and Perez on soft tyres towards the end of the race and 0.053s separates them in favour of Perez.
Max Verstappen's eventual fastest lap, which secured the championship point on offer, was a further 1.3s faster than Bottas and Perez thanks to a later switch to soft tyres when less fuel was left in the tank, further underlining the true potential of the Red Bull.
Undoubtedly, the Mercedes car looked after its tyres better, allowing Hamilton to keep the pressure on Verstappen and Mercedes push home a strategic advantage.
"I think the reality is whatever we'd have done they just had a faster car with slightly less tyre degradation than us today," Horner said.
"We've got to take the positives out of the weekend that we've managed to push Mercedes this close at this circuit -- at a track where they were a long way ahead of us last year and one that's been a strong one for them over the years.
"We have to take these positives into the next race in Monaco."
Shovlin added: "We were able to sit behind them, and when you are the lead car and someone can sit on your gearbox for a whole stint, it's not normally good news.
"But we are still at the stage of the year when you are collecting data across the different tracks, but it does seem to be a trend that we have a slightly more neutral car, there's seems to be a bit harder on the rear tyres over a stint whereas we are using both axles quite well.
"We'll see with some more data whether that is really a feature of the car or just down to how we are setting the car up here."
But from behind the wheel of the second-place car the answer was obvious.
"We just need a faster car, it's very simple," Verstappen said.
"Then you don't need to get into a [strategy] situation like that. That's what we have to focus on."
Perez leaves Red Bull on the back foot
The race was the perfect example of why Red Bull needs Verstappen's teammate to be fighting at the front. Half of the reason Verstappen was so vulnerable was that Mercedes was effectively fighting with two cars against one.
Perez qualified poorly on Saturday and spent much of the race behind McLaren's Daniel Ricciardo. He turned in a great move to get past him for fifth position, but he will know as well as anyone he could be doing much better in that car.
Perez has started fairly underwhelmingly at Red Bull but it's early days to suggest he is in the same situation Pierre Gasly or Alex Albon found themselves in when they were Verstappen's teammate. However, given Perez's stellar career until this point, it's also worth pointing out the Mexican was expected to be a lot stronger out of the gate than he has been.
Horner still has faith Perez will join the fight at the front soon, but, as he did a lot last year, hinted that the Mexican could have put Mercedes under pressure with a better performance overall.
"I think it's coming together for him," Horner said. "He had an off day yesterday, he was compromised in the race behind Daniel. He didn't manage to make the headway at a track where it's so difficult to pass.
"Of course we desperately need him to be in that gap so Mercedes don't have the strategic options that they had today. But I'm convinced that will come for Checo as he gets more confidence and time in the car."
Norris accepts his warning
Lando Norris was the standout performer of the first three races, but this one looked a little more ordinary for the British driver.
He finished eighth and was given a warning - a black-and-white flag - late in the race for what appeared to be a very aggressive defensive manoeuvre on former McLaren teammate Carlos Sainz.
The Ferrari driver had a huge tyre advantage after a late pit-stop and was always going to get past. As Sainz closed in at Turn 1, Norris changed direction dramatically in a bid to hold position, something which is a big no-no in the rule book.
Norris insisted it was simply a spot of over-enthusiastic driving rather than anything malicious aimed at his old teammate.
"I was defending to Carlos, and I moved over and then I moved again slightly which is not allowed to do," Norris said after the race. "I didn't mean to do anything aggressive.
He added: "I just went for my line and I moved a bit too much. [It was] a fair warning." Norris' teammate Daniel Ricciardo recorded his best finish for McLaren so far. After holding Perez at bay for half the race, he held on to sixth position, keeping Ferrari's Carlos Sainz at bay at the end.
Despite Sainz not getting past Ricciardo, it was a very encouraging weekend for Ferrari. The team looked like the strongest midfield team on outright pace.
It might be easy to forget sometimes now he's not in a race-winning car, but Charles Leclerc is a supreme talent. He spent the first half of the race running in third, having got past Valtteri Bottas on the opening lap.
Bottas got back past when the pit strategies played out later in the race, but it was a standout performance by Leclerc. This season his finishing positions have been sixth, fourth, sixth and fourth.
Sainz finished seventh in the other Ferrari and although he was unable to get past Ricciardo in the final laps, the race seemed to confirm the big step forward Ferrari has made from last year to this season.
Norris said people have been wrong to downplay Ferrari's pace.
"The Ferraris have been good all year," Norris said. "I do not know why people underestimate them so much.
"Ferrari have been one of the quickest cars in terms of cornering all season. So when you come to this track which has fewer long straights like Imola and so on, and then they are quick.
"They've been quick all season. We knew that there were going to be particularly good here."