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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Thomas de Gendt has attacked the course, because the Belgian simply doesn't know how to do anything but attack.
He cruises over the line just under a minute down on Michael Hepburn's leading time.
Image source, Getty ImagesMissed a belting stage 19 yesterday?
While you're waiting for Geraint Thomas to roll down the start ramp, let our Bespoke at the Tour de France podcast get you up to speed (while still reading this live text of course).
Tom Fordyce, Rob Hayles and Gareth Rhys Owen will be on air with live commentary from around 15:00 BST.
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Peter Sagan cruises over the line 5mins 48secs down on Michael Hepburn's leading time.
It was all about just getting round unscathed for the injured green jersey today.
Image source, GettThe course did look to be drying after an earlier shower but a few drops of rain are falling again now.
The GC riders could be battling the conditions when they go off in about an hour and 20 minutes.
Image source, ReutersJonathan Castroviejo is zipping towards the finish line...he's going to fall slightly short of the leading time.
And the Spaniard comes in just under nine seconds down on Michael Hepburn. It's more than good enough for second as it stands though.
Jakob Fuglsang - 15:07 BST
Bob Jungels - 15:09
Ilnur Zakarin - 15:11
Nairo Quintana - 15:13
Dan Martin - 15:15
Romain Bardet - 15:17
Mikel Landa - 15:19
Steven Kruijswijk - 15:21
Chris Froome - 15:23
Primoz Roglic - 15:25
Tom Dumoulin - 15:27
Geraint Thomas - 15:29
BMC's Stefan Kung rolls down the start ramp.
Kung is the Swiss national time trial champion and perhaps an outside bet for the stage win today.
TV pictures pick up Julian Alaphilippe warming up on the turbo.
The Frenchman thankfully has not opted for an all polka dot skinsuit, wisely going for all red shorts instead.
He has dominated the mountains classification and, barring catastrophe, will pull on the polka dot jersey in Paris tomorrow.
Team Sky's Jonathan Castroviejo has lost a bit of time to Michael Hepburn over the second section and is 10 seconds down heading into the final part.
Image source, ReutersTom Dumoulin also had to get a new world time trial champion skinsuit made - because he and his team somehow managed to lose the first one.
"I gave my skinsuit to the team truck so I didn't need to carry it around for three weeks," Dumoulin told ITV4.
"Apparently it got lost so it was a bit stressful earlier.
"But our clothing sponsor brought in a new one for me that they made this morning."
Fortunately for Geraint Thomas, he won't have the same see-through skinsuit situation as Luke Rowe.
That's because the race leader was fitted with his own bespoke all-yellow skinsuit last night...
Image source, CyclingimagesTeam Sky's Jonathan Castroviejo, the Spanish national time trial champion, has blitzed through the first time check just a shade quicker than current leader Michael Hepburn.
Image source, ReutersRowe did also have some advice (and maybe a warning?) for his team-mate Geraint Thomas...
Team Sky's Luke Rowe, speaking to ITV4: "There are a few dodgy bends but it's pretty straightforward - I didn't recon it or have a following car so was just riding it blind.
"But it's a tough course - the Tour de France is far from over.
"Geraint has been here before the Tour to recon it and has ridden this morning so he's now ridden it three times in total and he knows the course better than I do.
"You've got to push on the climbs, take the descents fast and stay upright."
Talking of skinsuits, Team Sky's mostly white outfit has turned out to be, er, pretty see-through in the rain.
Luke Rowe had a laugh about it at the finish, telling ITV4: "This skinsuit is a pretty kinky outfit - you can get away with it when it's not wet but not in this weather."
Image source, Reuters
Image source, Getty ImagesPeter Sagan has not long rolled down the start ramp.
The world champion crashed on Wednesday and had to battle through yesterday's brutal stage to make the time cut.
He made it with time to spare and afterwards said it had been his hardest day on a bike, adding he might well have just packed it in, were he not wearing the green jersey as leader of the points classification.
But the Slovak fought on and just needs to nurse himself through this time trial and cruise into Paris to win a record-equalling sixth green jersey. He looks a bit too injured to contest for the win in Paris, but you never know.
He's also not bothered with a skinsuit today.
Here is the current top five of all the riders to head off so far...
The top four on GC could well finish in the top four on the stage, although perhaps in a different order.
Michael Hepburn has had something to say about that though - the Australian has laid down a very testing marker, heading round the 31km course in 42 minutes 15 seconds.
The Mitchelton-Scott rider was part of the Aussie team that finished second to Geraint Thomas' GB squad in the team pursuit at London 2012.
Image source, Getty ImagesEven if Thomas does have too much of a gap for anyone to close, the race behind him is set to be a belter.
Dumoulin, Roglic, Froome finished in that order at the world time trial championships last year and are covered by just 32 seconds.
A time trial at the end of a Grand Tour is a different beast to a one-off event - how are their legs after all that climbing?
Could Roglic overhaul Dumoulin to finish second? Can Froome ride his way back onto the podium?
Image source, Getty ImagesGeraint Thomas leads Tom Dumoulin by 2:05 with Primoz Roglic at 2:24 and team-mate Chris Froome at 2:37.
Dumoulin is the world time trial champion and may well take back time on Thomas today.
However, Thomas is no slouch against the clock, having won the opening time trial at the 2017 Tour, albeit over a shorter distance.
Barring a crash or a series of mechanical issues, Thomas should have enough of a buffer.