Vettel comes off the pace in the middle sector and will come into the pits - he's already secured the best time going into qualifying, but with barely a cigarette paper between him and Alonso we could be in for a barnstorming qualifying session this afternoon. Join us for that at 1pm BST!
Free Practice 3
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It's the end of the session, and Vettel is still out there with a chance to pull off one more quick time...
Nobody else bothering the top three as the clock ticks down to 0:00 - Maldonado was on a good-looking lap, but locked up into the final chicane as we've seen so many do today.
Vettel has come round for a flying lap now - and he's bested Alonso by a tenth of a second! It's a 1:48.327, the fastest time of the weekend so far by over a second.
Button has now gone fourth fastest now - nice lap from the McLaren man.
Raikkonen goes out on a flying lap on the medium tyre now, but he's over half a second slower than Alonso. ALonso's lap appears to have been genuinely very quick.
Alonso clocks 1:48.432 seconds, also on the medium tyre - he's fastest man so far by seven tenths of a second, and 1.4 seconds better than he was on the hard tyre.
Alonso six tenths up on Sutil half-way through the lap!
1:49.135 for Adrian Sutil as he goes out on the medium compound tyres - and he's quickest! But Alonso is now on a good-looking lap...
Adrian Sutil out on a flyer now, and looking good - he's fastest so far with just the final sector left.
Lewis Hamilton just seventh on the timesheets this morning, still not happy with his set-up.
Vergne still top of the tables, and he's told over the pit radio that his team think he's a genuine 0.8 seconds a lap faster than cars not running either Ferrari or Renault engines.
Vettel's form this morning - and that of sister team Toro Rosso with a Ferrari powerplant - is ominous for rivals hoping to pick up points on him this weekend.
Sorry Fernando, someone keeping you up?
Vettel is coming around at the end of his lap, and he's second fastest, 0.277 down on Vergne, despite his best attempts to look like he's driving in a rally.
Vettel comes off the track and goes into the dirt at the top of the hill at the end of the Kemmel Straight - mud flies everywhere, all over the track. Tsk, tsk. Mucky pup. I hope he'll go out with his broom after the session and help clean up.
Felipe Massa talking to his mechanic in the garage on the TV monitors - and brilliantly, the mechanic takes care to cover his mouth while chatting to make sure nobody from one of the other teams can lip read him!
Pastor Maldonado becomes the latest man to almost go into the sidewall in that section between turns 13 and 14.
Webber comes in just over 1:50 with that flying lap, and given how neat he looked throughout I'd suspect that was a decent time on a fuel-laden car.
Webber looking very tidy throughout here....
Mark Webber has been in the pits for a while but is back out now and on another timed lap.
Di Resta locks up his wheels once again going into the final chicane, the famous Bus Stop. He looks like he's trying to drive a bus right now, the amount he's sliding all over the place.
Raikkonen struggling for grip on that lap, particularly in that final section - and he's a good five seconds slower in that lap.
Kimi Raikkonen has dipped into the pits but is back out now and looks like he's on a heavier fuel load this time - much slower than his earlier efforts.
Now Sutil is also complaining to his engineers over the radio about his tyres. Force India struggling right now.
Di Resta loses grip yet again - the Force India driver is struggling like nobody else in this session right now.
Toro Rosso's Jean Eric Vergne has pulled out a blistering lap from somewhere, a 1:49.479 to leap to th etop of the standings.
Nobody has gone quicker than Raikkonen still - Alonso is on a flyer right now though...
Lewis Hamilton has spun off again! He was heading into the final chicane once again, and did a complete 360 this time. The Mercedes clearly struggling for a bit of grip this weekend.
Massa is now out onto the circuit as well - and he too slides off at turn 13, a carbon copy of Di Resta's blunder earlier. Both men lucky not to go into the side wall.
Raikkonen comes around for another lap - not quicker than his first - but he's lost a bit of the back of his car onto the start-finish straight. Not sure what's happened there.
Spa's Eau Rouge corner is perhaps the most famous in F1, but Ferrari's Felipe Massa has complained that it ain't what it used to be.
Button has pulled into the pits and mechanics are furiously working on his rear suspension - his rear wing is off and people are looking glum.
Paul Di Resta comes off again! The Scot locks up under braking once again, this time at turn 13.
Kimi Raikkonen comes out and shows his class immediately with the fastest lap of the session so far, a 1:49.759.
Still dry right now, but possible thunderstorms are predicted for the qualifying session later this afternoon. Tomorrow's race forecast is currently fine.
Bottas still the fastest man out there, Button a quarter of a second slower, but of course it's very early days.
They're all at it now! Within a few seconds of Hamilton running off, Rosberg and Di Resta skid off at the last corner too. Heavy fuel loads and cool tyres probably to blame.
Hamilton locks it up going into the final corner! He slides straight off the track at the chicane , but luckily there's plenty of run-off space and he re-joins safely.
Lewis Hamilton is now out on the track as well - he struggled yesterday, but is doing okay so far this morning with a good start to his lap...
Button, incidentally, is one of several drivers whose future is up in the air for next season. It's that time of the year in F1...
It's a 1:50.088 for Button.
Jenson Button is now out on the circuit too... can he do any better?
Bottas has improved to 1:49.806, that's within half a second of Vettel's best lap on Friday afternoon.
It's a 1:51.140 for Bottas, while Maldonado has also completed a full lap of 1:52.479.
Looks like Valtteri Bottas of Williams will be the first man to clock a time this morning...
Mark Webber among the drivers out on the track right now, but nobody has set a lap time yet.
The big story of yesterday was the blow-outs that sparked memories of the chaotic British Grand Prix - but Pirelli believe they have found out what happened.
Several cars come out onto the circuit immediately, with good dry conditions on the track.
And we're under way at Spa!
Good morning and welcome to our LIVE coverage of the final free practice session ahead of the Belgian Grand Prix.