• Lewis Hamilton led a Mercedes 1-2 in the second practice session.
• The session was stopped a few minutes early when Alfa Romeo's Antonio Giovinazzi's car suffered
• Vettel also had engine failure, causing his car to leak oil on the track.
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Lewis Hamilton led team mate Valtteri Bottas in a Mercedes one-two in practice for Formula One's 70th Anniversary Grand Prix at Silverstone on Friday.
The six-times world champion, chasing a fourth win in a row on Sunday to stretch his 30 point lead over the Finn, lapped with a fastest time of 1min25.606 seconds using medium tyres on a hot but cloudy afternoon.
Bottas, who had been fastest in the day's first session as drivers got to grips with Pirelli's softer tyres, was 0.176 slower.
Hamilton won last Sunday's British Grand Prix at the same circuit from pole position and despite a last lap puncture.
With 87 career wins, the Briton is closing in fast on Ferrari great Michael Schumacher's all-time record of 91 set between 1992 and 2006.
Red Bull's Max Verstappen was best of the rest in the morning, 0.727 off the pace, and Renault's Australian Daniel Ricciardo filled that slot in the afternoon with the Dutch youngster fourth.
Racing Point, fined and with 15 points deducted after stewards upheld a Renault protest, looked quick with Lance Stroll ending the day fifth and experienced German stand-in Nico Hulkenberg sixth.
Hulkenberg, replacing Sergio Perez after the Mexican contracted Covid-19 and then tested positive for a second time, was fourth in the opening session.
Ferrari's Charles Leclerc was fifth and seventh fastest respectively but team mate Sebastian Vettel suffered an engine failure in the afternoon and ended up 14th.
The title of Sunday's race commemorates the first world championship grand prix which was hosted by Silverstone in May, 1950.
Mercedes have a horseshoe symbol on their cars in honour of the late Stirling Moss, who raced with the emblem in the early years of his career. Moss competed at Silverstone in 1950 in a Formula Three race.