Valtteri Bottas will be starting from at least sixth position at the British Grand Prix after Mercedes confirmed an unscheduled change of gearbox.
Lewis Hamilton suffered the same penalty in Austria last weekend and cut a very dejected figure after only being able to rescue four places from P8 after his gearbox change.
Bottas had put himself right into the title mix following his victory at Spielberg, but the Finn, fastest in both FP1 and FP2 at Silverstone, now faces a daunting task in Sunday's race to keep applying the pressure on World Championship leader Sebastian Vettel, who has a 20-point lead.
The demotion also leaves Hamilton exposed to the two Ferrari drivers, who can potentially pen the Brit in with an over-cut and under-cut strategy.
Mercedes confirmed via Twitter that a five-place grid penalty would come into effect on Sunday.