Williams' head of performance engineering Rob Smedley admits the team got Valtteri Bottas' race strategy completely wrong and were powerless to prevent him from tumbling down the running order in the closing stages at Hockenhiem.

The Finnish driver was on an aggressive two-stop charge but it failed to provide the optimum strategy and with Williams reacting too slowly to alter Bottas' race, the team were forced to toil and watch him slip from seventh to ninth in the final few laps.

Smedley says Williams had been relying on tyre data which proved to be inaccurate in the warmer than expected conditions and confirms the team has taken full responsibility for the mistake.

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"With Valtteri, we tried a strategy which clearly didn't work," Smedley said. "We deployed the wrong tactics in the race, which is something we've got to learn from.

"As a group of people, we get it right most of the time, but today we didn't. We thought the tyres would go to the end but they didn't and so ninth was the best we could achieve, unfortunately."

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Williams' frustrating German Grand Prix got off to a terrible start when Felipe Massa got tangled up with Renault's Jolyon Palmer on the first lap and after picking up a problem he was eventually forced to retire on lap 36.

"We were trying to understand what the problem was as Felipe was completely off the pace and complaining about the car," Smedley said. "There was no alternative other than to retire because he was towards the back of the field and struggling.

"It hasn't been a great day but this is where we see the mettle of everyone moving forward and make sure we don't let our heads go down. We'll carry on improving and trying to do the absolute maximum that we can do with the car that we've got. We'll keep pushing on."

Williams saw Force India close the F1 world constructors points deficit down to 15 in the battle for fourth behind the dominant Mercedes, Red Bull and Ferrari squads.

Germany has capped a frustrating month for Williams who as a squad picked up just six points over four races (Bottas claiming ninth in Austria, Hungary and Germany), while Massa has failed to score a points finish since Azerbaijan.

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