Postpublished at 16:10 British Summer Time 28 July 2018
Meanwhile, Geraint Thomas appears to have eased off slightly in the final section.
Not that the stage win matters. He's approaching the line now, certain of Tour de France victory.
Geraint Thomas third on stage 20
GB's Thomas set to win title in Paris on Sunday
Chris Froome moves up to third overall
Tom Dumoulin wins stage and maintains second overall
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Jack Skelton
Meanwhile, Geraint Thomas appears to have eased off slightly in the final section.
Not that the stage win matters. He's approaching the line now, certain of Tour de France victory.
Right, er, the TV clock seems to indicate Tom Dumoulin got there just ahead of Chris Froome's time.
It's so close though that it's going to be checked again.
This is going to be so close...
Tom Dumoulin is flying towards the finale.
Can he win the stage?
Chris Froome watches on in the hotseat.
Primoz Roglic is approaching the finish line but will lose in excess of a minute to Chris Froome and thus his third place.
Rob Hayles
Ex-GB cyclist on BBC Radio 5 live, in France
Thomas' legs are completely running out but he's got that buffer. I think he's gone a little too quick over the first half of the race. He is hurting.
Sure enough, Chris Froome storms through into provisional first place.
The four-time winner blasts over the line, 52 seconds quicker than team-mate Michal Kwiatkowski, who gives a knowing wave to the TV camera as he vacates the hotseat.
That was a superb time trial from Froome.
Mikel Landa comes through over two minutes down on Michal Kwiatkowski - he's lost sixth place to Romain Bardet.
Steven Kruijswijk comes home in a very decent time and stays fifth.
But Chris Froome is storming up the run-in not far behind the Dutchman...
Primoz Roglic is fighting his way up a veritable wall, so tough is the gradient of this climb.
The Slovenian is seeing a podium place slip away but it's still been a superb race by the former ski jumper.
Tom Dumoulin now hits the climb down the road. Can he storm it home?
A smattering of boos greets Chris Froome as he attacks over the crest of the climb and into the final 3km.
He's riding himself back onto the podium here.
Romain Bardet comes home - it's an admirable showing from the Frenchman, just 1:06 down on Kwiatkowski.
He's certainly fared better than the likes of Nairo Quintana and Mikel Landa.
Quintana came down 3:15 down on Kwiatkowski and Landa is struggling out on course.
Dan Martin comes through 1:50 down on Michal Kwiatkowski, who still leads for now.
Geraint Thomas is churning a huge gear up the ramp to the second time check.
He flies through 12 seconds up on team-mate Chris Froome.
A third stage win is on the cards here.
Geraint Thomas should be at the second time check soon.
The Welshman is blitzing this.
Chris Froome will not be taking second place off Tom Dumoulin though.
The world time trial champion comes through the second time check just two seconds back on Froome and is very unlikely to lose 30 seconds in this final section.
Primoz Roglic comes to the second time check nearly 50 seconds back on Chris Froome.
That is an insurmountable gap and Froome will take third place back off the Slovenian.
Roglic was second at the world time trial championships last year but a time trial at the end of a Grand Tour is a brutal, different beast.
Ilnur Zakarin has put in a superb effort here but falls short of taking the lead.
He comes home just under 12 seconds down on Michal Kwiatkowski, good enough for fourth overall as it stands.
He'll definitely retain his top 10 on GC and come move above Nairo Quintana.
Chris Froome is perhaps channelling all his frustrations from this Tour into this time trial.
The four-time winner zips through the second time check nearly 28 seconds faster than previous best Ilnur Zakarin.
Bob Jungels is driving towards the line, threatening Michal Kwiatkowski's time...
But he just misses out on taking the provisional lead, coming home 1.81 seconds downon the Team Sky rider.
Rob Hayles
Ex-GB cyclist on BBC Radio 5 live, in France
Thomas has got to take it easy on the bends. As long as his race radio is working they will be giving him the information he needs and as last man on the road he knows what he needs to do.
He has to back off on the bends because it could all disappear in a moment.