In a Formula One season dominated by Mercedes, Sunday's Abu Dhabi Grand Prix was an anomaly.
In a straight fight and on a track where Mercedes has won every grand prix since 2014, Red Bull took not only pole position but also a convincing victory.
It was only the team's second race win this year, which might not seem like a reason to get excited, but its timing and the manner in which it was delivered could hint at a more competitive season next year.
For too long F1 has seen one team dominate -- be it Red Bull between 2010 and 2013 or Mercedes from 2014 onwards -- and the prospect of a genuine title fight is tantalising.
But those who have watched Mercedes' domination of the past seven years will also recall numerous false dawns for rival teams.
The difference this time around is that the basis of this year's car design will be used again in 2021 to save costs.
The freeze in development does not extend to the car's aerodynamics, which will be governed by a new set of regulations aimed at reducing downforce to ease the load on the tyres after a number of failures this year.
But a solid platform at the end of 2020 should provide a solid start to the 2021 season, which is something Red Bull's title campaigns have been lacking in recent years.
All this has led to the question of whether Red Bull's win in Abu Dhabi was a sign of things to come or a mere blip in Mercedes' domination of the sport...
Did Mercedes simply get it wrong in Abu Dhabi?
In a word: yes.
Look at the qualifying results in Abu Dhabi and it's not just Max Verstappen's pole position lap that stands out.
In a year when Mercedes has regularly held advantages of more than 0.7s over the rest of the field, Lando Norris' McLaren was just 0.2s off the pace of Valtteri Bottas and Lewis Hamilton.
While Norris deserves plenty of credit for a fantastic qualifying lap, McLaren has not suddenly closed the gap to Mercedes to a couple of tenths.
A more logical conclusion is that Mercedes slipped up and Red Bull and McLaren took advantage.
Both Mercedes drivers complained of understeer -- when the front tyres fail to offer the necessary grip to match the driver's steering input -- in qualifying and in the race, and the lack of balance in the car's setup was a key factor.
The Yas Marina Circuit in Abu Dhabi has a varied lap, with a fast first sector and a tight final sector. The perfect setup is a neutral one that allows the driver to push with confidence in both and look after the tyres.
By their own admission, Mercedes' engineers were lulled into a false sense of security by a promising Friday practice in which the car seemed well balanced.
Satisfied with the way the car was handling, Mercedes devoted a large part of its track time on Friday evening (when the conditions are the closest match for qualifying and the race) to preparations for next year.
Mercedes has already won both titles this year, so understandably the development focus has been on 2021 for some time.
For the second practice session on Friday, Pirelli supplied each driver with a set of 2021-spec tyres, which have a different construction in order to prevent punctures and allow teams to run the tyres at lower pressures.
Getting the most from the new tyre design will be key to success in 2021, but Friday was the last chance to try the new construction ahead of the reduced number of days of preseason testing next year. Put simply, every lap on the tyres had the potential to unlock a tiny bit of understanding and performance next year.
But somewhere in the changing track conditions between Friday and Saturday, Mercedes lost the thread that has stitched its 2020 title campaign together, and when qualifying rolled around on the 2020 tyres, the car was not operating as expected.
"The surprise came from the fact that on Friday we looked all right," Mercedes chief trackside engineer Andrew Shovlin said on Sunday night. "We did our own programme on the 2021 tyres, and we were keen to focus a fair chunk of our effort on that.
"If we were struggling [for performance] on Friday, then we might have said that we'd spent too much time on those tyres, but we weren't and we were very quick. So to be honest, on Friday night we were fairly relaxed where we stood and the surprise was on Saturday morning when we hit the track and we were slow.
"We hadn't changed a lot; we know that the soft tyre is a fiddly tyre, sometimes we get it in a good window and sometimes we don't, but the whole of Saturday was a struggle.
"To be honest, I think we did well to get the cars second and third [on the grid] and within a sniff of being on pole."
Had Bottas found the 0.025s to outqualify the Red Bull on Saturday, it could have been a different story in the race, but as things played out, Verstappen made a clean getaway from pole position and led through Turn 1.
The problems Mercedes experienced in qualifying then caused further issues in the race and were exacerbated by a Safety Car period on lap 10 that encouraged the top three drivers to pit on the same lap, stripped the race of any strategic variation and forced a long second stint on the hard tyres.
"This was a race where, if you wanted to win it, you had to be on pole," Shovlin added. "In the race we were optimistic that our race pace is normally strong, our [low tyre] degradation is normally strong, but as it unfolded it became painfully apparent to us that we didn't have the speed to challenge Red Bull and so we just sat there and finished second and third and couldn't really make their lives difficult.
"It was a bit of a surprise coming into the race weekend. They did a good job, and we will look at what we could have done better. But the big surprise for us is that on Friday we looked to be in good shape and evidently from qualifying and the race we weren't."
Much was made about concerns with the reliability of Mercedes' hybrid system during the race, and it's true that the engineers reduced the workload of the MGU-K after a series of failures on customer cars at recent races. But the team estimates the lap time loss was less than 0.1s (and only in the race, not in qualifying), meaning it had little bearing on the final result.
Part of Mercedes' success in recent years has been its ability to learn from its mistakes, and no doubt Sunday's defeat will be analysed at length to find answers.
"Fundamentally, today we didn't have the best car," Shovlin added. "We need to look at whether we could have got more out of it, whether it was an issue with where we positioned it in terms of setup or whether it's something to do with this circuit that suited Red Bull.
"It's something we don't understand right now, and it is something that will sit on the job list of things for us to get stuck into in the next week or so.
"The whole weekend just looked like Red Bull had the upper hand by a bit, and for us, unless we were on pole, we were never going to win this race today. We didn't have a difference in car pace, so in a way it was lost yesterday, which was a close battle. But looking at today, unless we had a car on pole, I think we would have struggled."
Can Red Bull make a habit of winning?
Sunday's result was the kind of performance Red Bull was hoping to deliver from the beginning of the season. There has always been a feeling that this year's RB16 is a quick car, but unlocking that pace consistently has been the issue.
Yet it seems that on the Yas Marina circuit the team finally hit the sweet spot for a whole race weekend.
As much as Mercedes struggled in Abu Dhabi, it should also be said that Verstappen looked truly dominant. Had Bottas or Hamilton been able to push him harder in the race, there's every chance he would have upped his own pace and had an answer.
Alex Albon, who has been more sensitive to vicious handling of the RB16 and has struggled all year, was closing on Hamilton in the closing stages, underlining the significant advantage Red Bull seemed to have in race trim.
"I think we've improved the car significantly and understood where those issues are," Red Bull team principal Christian Horner said. "Hopefully that can be further addressed as we go into next year.
"We need a car that performs at a whole variance of circuits, which Mercedes has been very good at producing, and that's where we need to be strong next year. We have got to be strong on all types of circuits across the 23-race calendar, but I think to take today's performance at a circuit like this into the winter is very encouraging."
Viewed another way, Red Bull's performance in Abu Dhabi was not such a big surprise. There have been glimpses of strong performances at the previous four rounds, and perhaps all the team needed was for Mercedes to hit a bump in the road for the reality of that performance to come into view.
"I think our pace last week in Bahrain was very strong; it's just a shame that we lost Max in the third or fourth corner," Horner added. "He missed out on the pole by 0.05s [at the Sakhir Grand Prix] and left Bahrain feeling frustrated.
"We've just been chipping away at the car, and over the last third of the year, we made genuine progress. We were unlucky in Imola; Turkey didn't go our way; the first Bahrain was decent; and the second Bahrain we were unlucky.
"And then here in Abu Dhabi, to be the first team to beat Mercedes in a straight fight at this circuit since winning it ourselves in 2013 is a great achievement and gives the whole team a huge amount of energy as we head into what will be a very short winter."
But there is one very large caveat to Red Bull's progress in recent races. In mid-October, Mercedes revealed it had stopped development of its 2020 car "a long time ago", meaning Red Bull has been chasing a relatively static target.
So while Red Bull has been chipping away at the gap, has Mercedes simply been working on a much bigger upgrade targeted specifically at the changes to the aero regulations for 2021?
It's clear that Mercedes and Red Bull have taken different approaches to the 2020-to-2021 transition.
Red Bull has continued to develop its 2020 car in the knowledge that any flaws ironed out on track this year will offer a better platform for next year, while Mercedes -- understandably content with the performance of its 2020 car after 13 race victories from 17 races -- has kept its development locked away in its wind tunnel and CFD (computational fluid dynamics) programme back in Brackley.
Arguably the ultimate Formula One car is not one that wins all the races in the season but one that makes a strong enough start to the year to allow you to switch focus as early as possible to its predecessor.
That's not to say that Red Bull hasn't devoted enough attention to its 2021 development back at its base in Milton Keynes or that Mercedes hasn't brought any 2021 development parts to the car to test this year, but if you were to put money on one of those two teams taking a bigger step over the winter, the safe bet would be Mercedes.
"The only thing I'd say to that," Horner offered as a counterargument, "is that there is obviously a significant amount of carryover in terms of gearbox, chassis and elements of the suspension.
"A large element of the car's performance is aerodynamic, and that can be altered for next year. Our philosophy has been whatever we learned this year can be carried into next year anyway.
"They [Mercedes] are a very strong team, they have great strength and depth, and we've seen that they have been bringing some components to the car, and of course we expect them to be very strong next year. But if we can build on this momentum, hopefully we can give them a harder time."
Only time will tell, but the past seven years has taught the rest of the F1 grid to underestimate Mercedes at their peril.