Hello and welcome to Friday practice for the British Grand Prix. The sun is out, we've got a new circuit and 24 drivers ready to hit the track in about 35 minutes - it should be an interesting session.

The big news overnight is that Bruno Senna has been replaced by Sakon Yamamoto for the whole weekend at HRT. We're still waiting on an exact reason why but we'll keep you updated as soon as we know.

It'll be business as usual for everybody else, but we'll keep an eye on McLaren's progress as it is testing its new blown diffuser today. Don't expect headline times straight away, as the first runs will be about checking reliability and how the exhaust gases affect the rear bodywork.

Williams also has a blown diffuser on its car, so we'll monitor the progress of Barrichello and Hulkenberg as well.

As always you can send any questions or observations through to the commentary team by clicking on the link at the bottom of this window.

We also have an extra 0.8 kilometres of track. The big question is whether it will improve overtaking, but we probably won't get an answer to that until Sunday.

The bad news is that even the backmarkers aren't that keen to get on with the action, so we could have a quiet first half hour after the installation laps are complete.

Virgin: "We are expecting this session to be very quiet. Maybe an install lap for Lucas and then wait. "

The lights have gone green and di Resta in the Force India is first on track. He's taking over Liuzzi's car for the first session but Tonio will be back in the car this afternoon and for the rest of the race.

Yamamoto is out on track alongside Button and Massa. Button desperately wants to win here this year, but his performance will probably be dependent on the new upgrade.

Button returns to the pits after his installation lap. He was taking it very easy and will now probably get out of the car and allow the team to make a few adjustments.

Nenad asks: "Do you think that changes to the Silverstone track (new Arena section) will favour RBR? They are very good in slower corners (Monaco GP)."

True, but they are even better in fast corners. There are two new and very fast corners called Abbey and Farm before they reach Village and The Loop (the slower ones). Those first two corners are nearly flat out, so it will be interesting to see who is quick through there - a bit like comparing the cars through turn 8 at Turkey. I expect Red Bull will still be very quick throughout this lap, in both fast and slow corners.

Ferrari has a hectic schedule in these two practice sessions: "It will be a very busy day with an intense technical programme. A lot of things to test for this weekend and and the next races."

The only drivers not to hit the track so far are Fairuz Fauzy and Timo Glock. Fauzy is in Trulli's Lotus for this Friday morning session.

Images from the pit lane show Glock stood on the pit wall and he doesn't look like he is about to go anywhere. Meanwhile, his Virgin team-mate di Grassi is heading out on track.

The track is still pretty dirty according to Petrov. Renault says: "Robert is back in the garage after his installation lap. Vitaly says that the track is very dirty."

A lot of work is going on at the rear of Fauzy's Lotus, he could face a long wait before hitting the track.

James offers his views on the prospect of two US Grands Prix: "Is Bernie just talking out of his bum or what? Two U.S. grands prix? The fan base is probably not here for even one, especially in Texas. New York/New Jersey? I would think the people in that area would have more important things do on a weekend than go to a race. I am thinking the largest portion of any crowd would be from foreign tourist as U.S. grands prix are at a bargain price usually compared to going to a European race and tickets will be much easier to get."

Button is out on track. The rear of that McLaren is already attracting a lot of attention in the pit lane, but F1 journalist Maurice Hamilton says Red Bull has responded with two van-loads of Red Bull updates arriving in the paddock this morning.

Button sets the first timed lap with a 1:37.994 but the track is still very dusty and we can expect that time to be beaten considerably throughout the day.

The grandstands are absolutely packed today, great to see such a huge crowd.

Watching Button, the track looks very bumpy in places and there were a few complaints about that during the recent MotoGP race earlier this year. The new sections of track, especially Abbey, looks particularly bumpy.

Latest news from the pits: Glock has a fuel pressure problem and Fauzy's car might be out of the entire session.

Button's fastest time is now a 1:35.580 ahead of Webber with a 1:35.958. Alguersuari is five seconds adrift and Yamamoto is 11 seconds off.

Bernie Ecclestone is having a conversation with Christian Horner on the pit wall.

Webber is now fastest with a 1:34.681 but comes up behind traffic on his next lap.

Alguersuari slides his Toro Rosso through Club corner while following his team-mate Buemi. Alguersuari is the fastest of the pair so far by about four seconds.

Schumacher is off the track at Village corner. He lost the rear of the car coming into the slow right hander as he tried to find the limit. A replay shows that Hamilton made a similar mistake, but managed to catch the slide and didn't actually spin the car.

Schumacher doesn't look deterred and is still crashing over the kerbs in his Mercedes. But he makes another mistake into Village for the second lap in a row.

Hamilton has a massive moment over the bump entering Abbey corner. He has to use the large run-off area there and rejoins the track. But it just goes to show that that corner is not straight-forward.

Di Resta also goes off the track at Abbey, and a replay shows a mistake from Barrichello exiting Chapel. Both drivers ran wide but no major damage done.

Hamilton finishes a long run, and reports from the pits suggest the rear of the car looks unaffected by the heat.

Rosberg is now the fastest with a 1:33.622, 0.187 up on Kubica and 0.283 up on Webber. I suspect we have yet to see a competitive lap from the McLarens or the Ferraris.

Massa runs wide exiting The Loop and has aborted his run. He wants a few changes made to the car.

Di Resta admits that he was having a bit of a problem over the bump heading into Abbey and suggests that a few changes might have to be made to the car.

Mercedes' Nick Fry said Schumacher was experimenting with different lines through the new corners and that could go someway to explaining his spin. Overall, Fry says well done to Silverstone on the new track.

Vettel is now fastest with a 1:32.762 but is immediately beaten by Kubica with a 1:32.705.

Vettel resumes his position at the top of the timesheets with a 1:32.280.

Tony asks: "Can you tell me why the teams have to wait till first practice to decide they need to change parts, and therefor waste valuable track time. How can they call for more practice time when their incompetence in preparation is obvious."

As I'm sure you know, there is no in-season testing anymore, and despite having computers and simulators, there is no comparison to actually getting a car out on track and seeing how it performs. Most teams do get it right - looking at Valencia, Mercedes was the only team that screwed up. If anything it is a good thing as it means the cars get out on track earlier in the session despite poor track conditions.

Charalampos: "How can it be that some drivers have 6 or 4 laps completed but no lap time at all at F1's live timing? Can they all be installation laps?"

Yep, that is explained by the drivers returning to the pits at the end of a lap an not crossing the finish line.

Jermaine asks: "Why are the Ferraris not improving as much as Renault and McLaren?"

That's a massive question and, of course, I can only speculate. Ferrari put a lot of development time into the F-duct earlier in the season and that didn't pay off as well as they had hoped. Now their focus has gone back to getting more overall downforce and it is expecting to progress a lot over the next three races as they refine their blown diffuser.

As for the times so far today, don't pay too much attention because, as Mike said, they are testing new parts and not necessarily going for quick laps.

Sutil was on a fast lap but ran wide at Village corner. And he returns to the pits with the third fastest time, 0.686 off Vettel.

Hiteshwar Jindal asks: "What do you think are the chances for Force India in this race and will they be able to catch up Renault?"

I'm not sure they will catch Kubica, but they should be quicker than Petrov. They have some improvements aimed specifically at this circuit and I think they should challenge for the top 10. They are also facing competition from Williams this weekend.

Hamilton is back out on track and he sets the sixth fastest time, 1.323 off Vettel. On his next lap he makes another mistake over the bump entering Abbey - that's at least the second time he has been caught out there. Maybe he need to raise his ride height a touch.

A sensor problem resulted in di Grassi missing out on a bit of track time but he is about to get back into his car.

Hamilton sets the fourth fastest time with his last lap. He had to lift through Abbey and change down a gear (we were expecting that to be nearly flat-out on a low fuel load), he also made a mistake exiting The Loop.

Alonso is currently 2.210 off Vettel and Massa is 2.831 slower than the Red Bull.

Adam asks: "Any word as to why Senna was dropped for this weekend?"

Nothing yet, we've been promised an explanation after this session so keep checking the website to find out.

Rajkumar Maheshwari asks: "Do you think it would be last year for Tonio Liuzzi at Force India and Petrov at Renault and do you think Kimi joining Renault?"

And Hiteshwar Jindal asks: "Tonio has not been living up to the expections of the fan or the team he is surely under performing and is not able to take the full advantage of what the car can do ... Is he being more defensive ? Should Vijay Mallya make in season change in the drivers line up? How about Narain ... he is been doing well and also he is the fastest indian in ratings as well? "

Tonio is contracted to the team for next season, and now that he has solved his chassis problem from earlier in the year, is doing pretty well. I don't suspect he will leave, the team was particularly impressed by his performance in Canada. The man most likely to come in at Force India is Paul di Resta but that would require Sutil to leave.

Karthikeyan is probably a bit old to return to F1. Kimi will only come back if he thinks he can win, I suspect he will stay in rallying. Petrov's position seems to be dependent on money, if Renault can land a deal with Mastercard (as has been rumoured) then maybe they will bring in another driver - possibly Sutil.

back to the track action and Schumacher is looking a bit more comfortable, Vettel is still fastest. We still don't think McLaren has done a proper lap yet.

Manuel says: "I think Kubica is the best driver this year, his performances relative to the Renault have been amazing; I'll say if he was in a Red Bull Vettel wouldn't be challenging him."

All the cars, with the exception of Kubica, are out on the track for one last run. But for the most part they are on old tyres, so don't expect a blistering pace.

"If Sutil is out I probably think that the team is not going to get the results .... sutil has always out qualified liuzzi and is certainly faster? And is he not happy with the team?"

I only speculated that because his contract runs out at the end of this year. If he wants to renew it I'm sure he will get it - I didn't mean he would be pushed.

Hamilton runs wide again at Abbey. He really threw the car at the corner on that last lap but couldn't quite hold onto it.

Chequered falg is out as Fauzy stops ion track. Vettel is on a fastest middle sector ...

Schumacher gets angry at his team-mate Rosberg who blocked him slightly on that last lap.

Vettel doesn't improve his time.

So Red Bull still looks quick, but I'm not sure we have seen a fast lap from McLaren yet. Ferrari also appears to be holding quite a lot back while Kubica and Sutil look strong again.

Rosberg appears to have the edge over Schumacher and Mercedes seem to have made some slight improvements overall.

More will be revealed in the afternoon session as teams attempt some soft tyre runs. Make sure you join us.