It was Geoffrey Chaucer who first claimed that all good things must come to an end.
And so, it seems, after three years of almost total domination, even if Mercedes reign isn't at an end it is quite clearly under threat.
All the claims and denials of sandbagging were brushed aside yesterday afternoon when Ferrari claimed its first front-row lock-out in nine years. Then again, perhaps that says more about Ferrari.
Admittedly, Valtteri Bottas was only 0.095s off Vettel's pace and might have taken pole but for a minor mistake on his final flying lap, whilst hell-for-leather Lewis Hamilton simply wasn't quick enough.
The Ferraris have pretty much dominated every session, with Kimi Raikkonen appearing much more on the ball than in previous races.
After weeks of badgering from the British media, Mercedes remains loath to issue team orders but Niki Lauda admits that the best way to combat Ferrari, and in particular Vettel, will be to say to whoever has the best chance today of challenging the red cars to be given priority, be it the team's Finnish or British driver.
Ferrari is also playing down the team orders discussion, at least publicly, but its best hope is for Vettel to disappear into the distance this afternoon and Raikkonen to ride shotgun in the opening laps. Whatever happens, at least one of the Ferraris has to be at the front by the end of the first sector.
At the start of the weekend the Red Bull duo claimed that fifth and sixth was the best it could hope for, absolutely everything riding on its massive upgrade due to surface at Barcelona.
However, even that best laid plan was scuppered by Felipe Massa who pulled out all the stops to split the two Austrian cars. When one thinks that only a few months ago the Brazilian had been pensioned off, the fact is that his driving this year has put much younger men to shame, and no we are not referring to his teammate.
Red Bull's plans have been further thwarted by the decision to change the engine on Max Verstappen's car overnight, the team subsequently discovering a problem with the water pump which was replaced only for the new pump to develop a fault, which means work is still ongoing only twenty minutes before the pitlane opens.
Indeed, his Indian Summer is reminiscent of another veteran who found a second wind on joining the Grove outfit, the ever popular Riccardo Patrese.
Behind this lot, and dismissing the likes of Sauber and McLaren for obvious reasons, it really is anyone's guess.
In all honesty, all the usual suspects involved in the midfield battle have been hit and miss this weekend, strong in one session and weak in the next, with disparity between the teams' drivers further muddying the waters.
Overall however, Force India looks good to be in for another points scoring finish, while Toro Rosso - despite Carlos Sainz' grid penalty - should be next up ahead of Haas, where the increasingly annoying Monsieur Moany must surely be pushing his luck.
As ever however, it could all be decided in the first few corners today, as that long, long run to the first corner will allow all sorts of leapfrogging and jostling before the unforgiving bottleneck that is Turn 1.
If nothing else, at least Vettel knows Daniil 'The Torpedo' Kvyat is around twelve spots behind this afternoon.
The pitlane opens and Vettel is among the first out. Verstappen also heads out, no doubt leaving a lot of Red Bull personnel with their fingers firmly crossed.
Air temperature is currently 26 degrees C, while the track temperature is 41 degrees. As was the case on Friday and Saturday it is bright and sunny.
With this very much a one-stopper, it's likely most will start on the ultrasoft before switching to the red-banded supers. However, Wehrlein, Ericsson and Vandoorne have opted to start on the red-banded tyres.
The field heads off on the warm-up lap.
"With just one stop expected, the start will be even more crucial," says Pirelli. "Note that positions 2,4, and 6 are on the 'dirty' side of the grid."
Alonso complains that his ERS is not working, he has no charge - and that's on the warm-up lap.
As the grid forms, Alonso's car stops at the entrance to the pitlane. He climbs from the car clearly disgusted, throws his steering wheel into the cockpit and walks back to the pits.
As a result the field heads off on an extra formation lap.
They're away. A brilliant start for Bottas, while Raikkonen is slow off the line, allowing Hamilton to move alongside. As they head down the main straight, Bottas leads Vettel with Raikkonen, Hamilton and Ricciardo three abreast with Verstappen in hot pursuit.
Hamilton moves from side to side, coming oh so close first to Ricciardo and then Raikkonen however, under braking for T1 the Finn gets ahead almost passing his Ferrari teammate in the process, while Ricciardo gets hemmed in and lose out to his Red Bull teammate and Massa.
Further around the lap, Stroll spins, the Canadian subsequently claiming that he was pushed by Hulkenberg on to the kerb and then spun.
At which point the Safety Car is deployed as Palmer and Grosjean appear to have clashed in the first corner, the Haas hitting the wall in the aftermath. On replay, Grosjean nudges the Renault in T2 which spins and then collects the Frenchman.
Behind the Safety Car it's: Bottas, Vettel, Raikkonen, Hamilton, Verstappen, Massa, Ricciardo, Perez, Stroll and Ocon.
The Grosjean incident is under investigation.
The Safety Car pulls off at the end of lap 3, as Hamilton asks his crew if there is anything he can do. He is told to bide his time.
Great re-start by Bottas who appears to catch his rivals off guard.
As Hamilton loses ground to Raikkonen, Ricciardo has a right-rear brake fire. The Australian slows and loses a heap of positions as he heads back to the pits his race clearly over.
Out front Bottas is setting a blistering pace opening a 1.8s gap over Vettel who is 2s ahead of his Ferrari teammate. Hamilton is 1.2s down on the Finn and 3.2s clear of Verstappen.
Ricciardo pits and the crew inspects the rear of his car. Eventually the Australia is told to switch off as the issue is terminal.
"I'm getting cut outs in power," complains Hamilton who remains 1.9s adrift of Raikkonen.
No further action to be taken over the Stroll/Hulkenberg incident.
Check out our Sunday gallery from Sochi, here.