Hello and welcome to ESPNF1's coverage of the final free practice session for the British Grand Prix. And the good news? It's dry, for now, so we will hopefully see the effect of the off-throttle blown diffuser ban.

The goalposts have been continuously moving when it comes to the diffuser blowing, with Christian Horner and Martin Whitmarsh having a bit of a row during the press conference yesterday afternoon. Whitmarsh was unhappy that Red Bull's Renault engines are being allowed to blow at a higher percentage of full throttle than McLaren's Mercedes engine. The reason is that the Mercedes burns fuel when blowing off-throttle, so produces more energy through the exhausts at a lower percentage than the Renault, which doesn't burn fuel. Confused? Thought so.

Tony Fernandes sensibly said that the ruling needs to be black and white, but the grey area is because the clarification has been brought in mid-season. If you've got an opinion on the matter - or have any other comments that you want to pass on - then you can get in touch with us using the link above or you can message Laurence in the Silverstone paddock via Twitter @ESPNF1_live.

And just when I thought I'd explained it, the ruling appears to have changed again. The FIA has issued a new directive this morning which apparently reduces the percentage at which Renault engines can blow (it was 50%) but doesn't prevent the Mercedes engines from doing so. Needless to say Christian Horner is not a happy bunny and is yet to officially comment. Laurence is on the case...

Alex Wurz on Twitter: "Funny - 4 mins after the rules came onto the noticeboard I saw [Christian] Horner and Adrian [Newey] storming through the paddock towards the FIA office. This is better than a soap guys!"

Ian emails in his views: "Looking in from the outside (down-under) it seems the FIA, with maybe a nudge from Bernie, are more interested in bums on seats and money and are doing all they can to even out what is becoming a one side championship. I can't believe rules can be changed at will, almost from race to race and now during race weekends. Next they will make Vettel carry a 20Kg. handicap!!"

Virgin (MarussiaVirgin) on Twitter: "Still dry here so there should be a lot of running in this session. The stands are looking pretty packed with fans"

We've got some dark and threatening clouds around the circuit, but sun in some areas.

And we're under way in this final session - we've actually got cars on track rather than just team principals arguing over engine usage. The two Virgin cars are first out, followed by Lotus and then followed by half of the grid.

Tonio Liuzzi has a half spin on his installation lap, but recovers to continue. His tyres will have been cold and gave him no grip as he eased on the power.

Paul emails in to say: "I just see it as a big whinge from McLaren, I read what they had to say in the press conference yesterday. According to Christian everything had been approved behind the scenes from the FIA ref: the types of mapping on how engines run from one manufacturer to another. Hence the reason Renault runs diff to Mercedes."

That may be true Paul, but McLaren were unhappy because the rules changed on Friday having been agreed on Thursday, and the updated regulations allowed Renault to 'cold-blow' at 50% of full throttle when it seems they were originally only ever doing it at 45% anyway. The FIA has now decided it is ignoring what anyone said after Thursday, therefore reverting to what was agreed before the weekend.

Nico Rosberg has a small fire while stationary in his pit box, but a fire extinguisher quickly puts it out..

We're still yet to have a timed lap, although Alguersuari is pushing on right now. There are a few spots of rain around the circuit at the moment, and Kovalainen is warned about them over the team radio.

Emo says on email: "I think those people of the FIA have no backbone! Normal is that the rules are given for the race year then they should stand to it and not change it around every race and the next would be that they change the rules in lap 47!"

We have our first timed lap of the morning! Alguersuari does a 1:38.936, followed by Trulli with a 1:43.682

Maldonado says it is raining at Stowe as he sets a 1:41.839

Schumacher goes quickest with a 1:36.228

On board with Paul di Resta and he was on a good lap but as he approaches Stowe he hits the rain and backs right off

Schumacher spins negotiating the Loop section, but turns the car around quickly and continues.

Kobayashi attacking the final two corners as the rain falls more heavily. Button is on a lap now too, but it's much darker towards the end of the lap

Christian Horner is still up at race control complaining about the latest directive. This could run all day...

Kobayashi goes second fastest and Webber third, 0.4s behind Schumacher

Mike Gascoyne on Twitter: "Raining slightly now, only meant to be light for a few minutes"

Webber goes fastest with a 1:34.699 while Kobayashi improves to a 1:35.432 and second place

Still some splashes of water on the on-board cameras, which means we haven't seen any improvements during the final sector.

Hamilton and Vettel are now out on track. Alonso has done just one run and is 13th fastest.

It's raining more heavily now, with many drivers diving in to the pits. But Hamilton has stayed out even though he's really having to struggle around slowly

F1Celi asks on Twitter: "Where does Ferrari and Cosworth stand with the newest changes to blowing?"

In all honestly, we're unsure. It's not clear whether they have been 'hot blowing' (introducing fuel) or 'cold blowing' (no fuel). The argument has been mainly between Mercedes and Renault, so we'll try and find out more.

The rain forced everyone back in to the pits for a while, but Kobayashi is back out now.

Only Liuzzi, Hamilton and Vettel are yet to set a time, although Ricciardo and D'Ambrosio haven't set competitive laps yet.

The BBC report that Mark Webber has a problem in the engine bay and Red Bull has taken the car apart.

Kobayashi is joined out on track by Rosberg, Alguersuari, Buemi, Heidfeld, Petrov, D'Ambrosio, Liuzzi and Vettel.

Webber is sat in his car watching the screens while mechanics work on the rear of the RB7.

Rosberg goes fastest on a 1:33.044 - he's on the soft tyres. So are Buemi, Alguersuari and Perez

Webber's session is over, so he's only had 6 laps of running in the dry. More bad luck for Mark and he'll have to be right on the pace from the word go in qualifying.

Perez pushing hard and he goes second quickest with a 1:33.264. Schumacher also seems to have a problem, his car is in pieces in the garage and he is not in it anymore.

Alonso has gone third fastest, he's 0.4s slower than Rosberg who has pitted. Only Rosberg, Alguersuari, Webber, Kobayashi and Schumacher are not on track.

Hamilton on the harder tyre, and his car seems very stiffly sprung as he bounces under braking

Vettel has gone fourth quickest, as Alonso improves to within 0.2s of Rosberg.

Di Resta has gone up to fifth. We've got a mix of drivers running on hard and soft tyres at the moment as they try to gather as much data in the dry as possible.

Perez has improved, and di Resta goes fourth above Vettel.

Alonso is on the harder tyre and he goes quickest with a 1:32.843.

Webber is back in his car with more work going on...maybe his session isn't over quite yet.

Vettel was on a good lap but lost time behind a Virgin in the final sector. Hamilton is told over the radio that he needs to find time in the first two sectors.

Kobayashi goes second quickest ahead of Rosberg, 0.17s behind Alonso. He was on soft tyres though, as is Rosberg right now.

Christian Horner and Adrian Newey are walking down the paddock looking very unhappy and not speaking to any media.

Schumacher is getting back in to his car as Kobayashi continues to push hard. He's just set the fastest middle sector so the soft tyres are holding up well for a decent number of laps.

Engine cover going back on Webber's car with 11 and a half minutes to go.

Massa going very quickly in sector one, as we see Horner talking to Helmut Marko in the garage. He still looks very unhappy.

Maldonado goes quickest with a 1:32.496 in the soft tyre

We're seeing more and more soft tyre runs now, with Button also on the softs but not very quick. Alonso is flying though

Button goes third, before Alonso sets a new fastest lap by over a second - a 1:31.464 setting fastest sectors all the way round.

Hamilton now on soft tyres but also off the pace. It could indicate high fuel loads, and there are also a few spots of rain on the camera.

Maldonado gets blocked by Rosberg, while Webber is back on track and has gone second fastest - 0.7s slower than Alonso

Vettel is going quickly now too, with a fastest first sector

Webber improves to within 0.4s of Alonso. Vettel also on soft tyres amd he goes quickest by just 0.063s

Schumacher was on a better lap but struggled with traffic at the end of his lap on soft tyres.

Massa has gone fourth, so the current order is: Red Bull, Ferrari, Red Bull, Ferrari

Both McLaren drivers are in the pits and out of their cars, so their work is done. Only Maldonado is also in the pits

Vettel again going quickly, on for another fastest lap

But he can't improve after losing time late on, more rain coming down.

Schumacher is improving on his previous best but is a long way down, he can only go 11th.

Sutil locks up in to Brooklands, while Vettel completes a final slower lap. That's all of the times completed and sees the order stand at Vettel, Alonso, Webber, Massa, Maldonado, Button, Kobayashi, Rosberg, Perez and di Resta.

Schumacher was 11th and Hamilton 13th but the times are unlikely to be the talking point during the next two hours before qualifying. Rain is in the air too, so there's plenty to look forward to today, make sure you join as for qualifying in a couple of hours. Thanks for all of your tweets and emails, sorry we didn't get to publish them all. We're back in 90 minutes, see you then.