Lewis Hamilton sixth as Nico Rosberg takes British GP pole
Mercedes' Nico Rosberg took pole in a topsy-turvy rain-affected qualifying session for the British Grand Prix as Lewis Hamilton was only sixth.
Hamilton was fastest with seconds remaining but erred in aborting his final lap and slipped down the field.
Red Bull's Sebastian Vettel took second ahead of McLaren's Jenson Button, Force India's Nico Hulkenberg and McLaren's Kevin Magnussen.
Both Williams and Ferraris failed to make it out of the first session.
Mercedes executive director Paddy Lowe said Hamilton had decided to abort his final lap because he was down after the first two sectors. It was a bad mistake because the last sector was drier and the drivers found huge time gains there.
"He felt the lap was worse and bailed out," Lowe said, "which was unfortunate because there was a lot of time left in sector three.
"These conditions are always tricky and the first run in Q3 sector three was down because it was wet, but in the last run the final sector was quicker because it has dried quite a bit."
It was the fourth race in a row in which Hamilton has made a mistake of one kind or another in qualifying and the errors are costing him dearly in the championship.
He came to Silverstone knowing he really needed to beat Rosberg to win the race to start closing the German's 29-point lead in the championship.
He admitted to BBC 5 live on Thursday that he had realised pole position was vital because overtaking is so hard in F1 this year.
He was devastated afterwards, admitting to BBC F1's pit-lane reporter Lee McKenzie: "I don't really have anything to say to you at the moment."
Rosberg said: "We came to a general conclusion to just go out and have a look, because if you don't go out you don't have a chance.
"I never thought it would be quicker. What made it was the last sector because the rest of the lap was slower, but I knew I had a chance to go quicker because I had lost three or four seconds [there] on the previous lap so I knew I could go quicker if it was drier."
Button said he was happy "like you could not believe. It's only third but for us after the last 18 months we had no chance of getting this result. It's nice to qualify so well in front of the home crowd."
Williams and Ferrari also badly misjudged the ever-changing weather conditions, missing the brief window of driest running in the first part of qualifying before rain returned.
Valtteri Bottas was 17th, ahead of Williams team-mate Felipe Massa and the Ferraris of Fernando Alonso and Kimi Raikkonen.
It was a huge turnaround for Williams, after they locked out the front row at the last race in Austria and Bottas took the final podium place ahead of Massa in fourth.
Alonso said: "It happens some times in this weather - 30 seconds before or later, you put the dry tyre on and you are in the hero part or the mistake part.
"We are here in the TV interview pen both Williams and Ferrari drivers so we did something wrong."
Asked what he could do in the race, Alonso said: "Enjoy. We will start at the back; we have some overtaking to do. We have zero points on the grid and nothing to lose."
Marussia's Max Chilton will start between Bottas and Massa in 18th after qualifying a career-best 13th but suffering a five-place grid penalty for a gearbox change.
His Marussia team-mate Jules Bianchi starts 12th, his own career best and also the highest grid position for the team since they entered F1 in 2010 as Virgin Racing.
Lotus's Pastor Maldonado, who qualified 15th, was excluded from qualifying because there was insufficient fuel in his car to provide the one-litre sample required by the regulations.
He will be allowed start from the back of the grid, but in front of the two Caterham cars of Marcus Ericsson and Kamui Kobayashi, which failed to set times within the required 107% of the fastest time in first qualifying.