A tidier lap by Sebastian Vettel and he lowers the benchmark with a 1:41.1. Several other drivers are out on the circuit now, sporting those snazzy purple boots.

And a bwoah jar for Kimi? 

Sebastian Vettel does a 1:41.404 on the ultrasofts to move into P1. He was fastest through the first sector but was scrappy through the middle sector. 

Good news Button fans (everyone?). Jenson is getting strapped into the car, playfully teasing the mechanic who is strapping him in by squeezing his muscles.

Image source, AP

Cars back in the pits with almost half an hour gone.

Sebastian Vettel is the first to head back out and he's got the purple walled ultra softs on. He's the first driver to give the quickest compound of tyre a go in this session.

The first famous sighting of the weekend goes to electro-popsters The Chemical Brothers - Tom Rowlands and Ed Simons - who are enjoying a look around the Red Bull garage. 

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BBC Radio 5 live sports extra

Don't forget you can listen to commentary on BBC Radio 5 live sports extra. Our chief F1 writer Andrew Benson is up in the comm box now as well, notepad and pen at the ready to analyse the long runs.

Image source, .

Image source, .

Lewis Hamilton: "Need to re-balance these wheels. They've got flat spots all over them."

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Nico Rosberg shaves half a second off his time to leap up to P3. He's just 0.037s down on Kimi Raikkonen, but has done his time on the slower compound of tyre.

Nico Rosberg, on softs, goes sixth with a 1:42.779. Nothing close to being representative from Lewis Hamilton yet.

Daniil Kvyat has limped his Toro Rosso back to the pits and during that time we've had several times lighting up the timing board. 

As it stands, Kimi Raikkonen is quickest. He's done 1:42.257. Valtteri Bottas is just 0.001s down in second. Both are on the super-softs.

Tom Clarkson
BBC Radio 5 live commentator

McLaren thought Jenson had an ERS problem this morning but when they looked at the data there was nothing wrong with the ERS. So what they've done is bring forward the power unit change that they do on the Friday night. They are just finishing off doing that and Jenson should be out in the next 10 minutes.

Allan McNish
BBC Radio 5 live Formula 1 analyst

Just looking at a replay as he just touches the kerb you see something coming off the side of the car, it looks like it came off the rim.

Some squiggly tyre marks end with Daniil Kvyat off the circuit in the final sector, facing the wrong way. He's had another puncture!

Times are coming down as Sebastian Vettel goes quickest with 1:43.337. However, Max Verstappen has now taken to the circuit and he subsequently goes a tenth of a second quicker.

Both those times were set on the soft tyres, but Kimi Raikkonen has slipped into some super soft boots. Expect him to go quicker soon.

What we really, really, really don't want for this weekend is Jenson Button to be beset with mechanical problems. Unfortunately, things are not looking good at the moment. His McLaren is up on the jacks and he won't be out any time soon.

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Fernando Alonso brings the benchmark time a touch, clocking a 1:44.624. 

Meanwhile, Sebastian Vettel is also out on the track. No sign of either of the Red Bulls or the Mercedes.

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Neil James: Jenson and the milk float at Silverstone,I was security and shielded him from the snappers when he decided to move an electric float   

Ben Hales: The cheeky grin he shot me when I tried to get him to sign a copy of his head & shoulders advert at Spa in 2011!  

Dave Rowbottom: The lovely piece by David Coulthard with him in the rallycross Beetle reminiscing about his father

Image source, BBC Sport