Lewis Hamilton took pole position in an extraordinary qualifying hour for the Hungarian GP, while title rival Sebastian Vettel lost out in the rain.
As a heavy rain downpour brought chaos and wiped out the advantage Ferrari had held in dry conditions, Hamilton endorsed his reputation as a master of the wet by taking pole by three tenths from Mercedes team-mate Valtteri Bottas.
“We couldn’t have expected this,” said Hamilton. “Ferrari have been quickest all weekend. Then the heavens opened and it was fair game.”
Mercedes had struggled in Friday’s heat when they overheated their tyres. But that characteristic of working the Pirelli tyres hard worked to the Silver Arrows’ advantage around a sodden Hungaroring while Ferrari faltered.
Beaten by Scuderia colleague Kimi Raikkonen, who briefly held provisional during a frantic Q3 shoot-out, Vettel was only fourth.
“We weren’t quick enough,” rued Vettel. “It was difficult. The laps I did were fine but just not quick enough. In the wet we aren’t as confident as in the dry.”
Critically, Hamilton pitted for a fresh set of wet tyres with just minutes remaining before returning to the sodden tarmac and finding just enough grip to beat the two Finns.
“We were lucky with the weather,” admitted Mercedes boss Toto Wolff. “In the dry we didn’t have the pace.”
Red Bull’s Daniel Ricciardo was caught out when heavy rain fell at the start of Q2 and failed to reach the shoot-out while Max Verstappen was just seventh behind Renault’s Carlos Sainz and Pierre Gasly of Toro Rosso.
A day after the team entered administration, Force India suffered their worst on-track result of the season as both Esteban Ocon and Sergio Perez failed to progress.
Stoffel Vandoorne’s struggles continued at McLaren with the Belgian eliminated at the first hurdle in the fifth successive qualifying session. Still without an internal Saturday win all season, Vandoorne will start his summer holiday 12-0 down to Alonso in qualifying and his F1 future in grave danger.
Sunday’s race, live on Supersport 2, begins at 2.10pm.