53km - The 2012 Tour de France champion crosses the line a massive 1:16 ahead of his team-mate Chris Froome to take the victory.
53km - Chris Froome moves into the top spot - momentarily. He's 34 seconds faster than Sanchez at the top of the standings, but that will be bettered very soon by Wiggins.
53km - Vincenzo Nibali has ridden a pretty solid time trial here. We haven't seen any of it, but the Italian Liquigas rider secures his place on the third ledge of the podium by finishing 1:48 down on the current leading time of Sanchez.
53km - We forgot about Jurgen van den Broeck - the Belgian is actually the next rider to finish. He comes home 2:31 down in 23rd. It will be enough to consolidate his fourth place in the GC.
16:31 - The latest checks show Wiggins leading Froome by 1:15 at the 48km point.
16:29 - We've hardly seen any pictures of Vincenzo Nibali on course - the cameras are, understandably, sticking more with the French riders and Sky duo. He's the next to finish.
53km - Luis Leon Sanchez is still in the lead after Tejay Van Garderen crosses the line to set only the fifth fastest time, 43 seconds down on the Spaniard. The American set off fast but faded. Still, better than Cadel Evans, who comes home 4:03 down in 48th.
53km - Haimar Zubeldia almost crashes on one of the final bends, but manages to save himself after his back wheel slipped. The Spaniard crossed the line 3:42 down on Sanchez.
53km - Pierre Rolland gives it his all in the closing straight... and it's just enough, he finishes 4:23 down on Sanchez - and he saves his 8th place by 8 seconds.
53km - Slovenian Janez Brajkovic comes home 3:48 down on the current target time set by Sanchez. Pierre Rolland has to finish within 43 seconds of the Astana man if he wants to retain his 8th place in Paris.
53km - Nicolas Roche crosses the finish 4:48 down on Sanchez and has lost his 11th place to Kloden, who could yet rise to 10th if Pinot doesn't post a strong time. Here's Pinot now. And he's 3:40 down - which should be enough to secure 10th place in his debut Tour.
30km - Wiggins completely demolishes Froome's time at the second check: 54 seconds quicker than his team-mate.
53km - Andreas Kloden comes home 1:58 down on the current leader Luis Leon Sanchez - it remains to be seen if it's enough for the German to rise into the top ten at the expense of Thibaut Pinot.
30km - Here comes Froome... and he's only four seconds faster than Sanchez at the second time check.
16:03 - Van Garderen passes by team leader Evans as he passes the 20km-to-go banner. The Australian is having a shocker.
53km - Denis Menchov can only post the 22nd best time at the finish, 2:37 down on current leader Luis Leon Sanchez.
16:01 - He may have slowed, but Van Garderen is still closing in on his team-mate Cadel Evans. He will pass him before the finish, for sure.
30km - Tejay Van Garderen has slowed since the first check - he did set the best time at the first one (before the Sky duo came along) but he's 24 seconds down in 4th at the second check.
15:57 - Wiggins looks so amazingly fluid and natural on a ITT bike. Once again, you could balance a bidon on his back - flat as a pancake.
30km - Pierre Rolland posts the 56th best time at the second check, 2:39 down on the current target time of Sanchez. He will lose his 8th place to Brajkovic today, but should stay in the top ten.
53km - Spain's Alejandro Valverde is a huge 6:45 down at the finish.
14km - Wiggins is 12 seconds faster than Froome at the first check - this is going all according to plan for Team Sky.
14km - Froome posts a monster time at the first check: 17:01 - that's 23 seconds faster than Van Garderen.
30km - Thibaut Pinot will struggle to keep his 10th place today: the French youngster crosses the second check 2:51 down on the Sanchez target time. Kloden could well be 10th tonight.
14km - Van den Broeck posts the 12th best time at the first check at 26 seconds on Van Garderen.
15:44 - Andreas Kloden is riding well. The German is 16 seconds down at the first check, whereas Nicolas Roche is having a shocker. He's already 1:30 down on Kloden and so will certainly drop from 11th in the GC tonight.
14km - We have a new leader at the first check: while Evans is having a shocker, his BMC team-mate Tejay van Garderen is rampant: 17:24 is three seconds faster than Sanchez, so the American has the new target time.
14km - Cadel Evans is a huge 1:10 down at the first check - that's 55th place. The Australian's horror Tour continues.
30km - Denis Menchov is 59 seconds down at the second check, in 10th position.
14km - Pierre Rolland is 59 seconds down at the first check in 38th position.
15:34 - Sean Kelly: "I think Wiggins will win this time trial today."
15:33 - Yellow jersey Brad Wiggins rolls down the ramp on a special black and yellow Pinerello. Nice. Tonight he'll know for sure that he is the 2012 Tour de France champion.
15:30 - Chris Froome is on course now. Can he give team-mate Bradley Wiggins a run for his money?
53km - Peter Velits comes home to take the second best time, 12 seconds down on Luis Leon Sanchez. That was a great effort from Slovakian.
15:27 - Italian Vincenzo Nibali has started. He's not a particularly strong time triallist, but he should be able to retain his podium position.
15:26 - We asked Richie Porte how his team-mates Wiggins and Froome would find the ITT: "They're going to go much faster than that. It's a beautiful course and there are a lot of people out."
15:25 - Belgian Jurgen van den Broeck rolls down the ramp for Lotto Belisol.
53km - Team Sky's Richie Porte is currently second at the finish after posting a solid effort, 35 seconds down on Luis Leon Sanchez.
15:21 - Tejay van Garderen on course now. The 23-year-old American was superb in the last time trial and will definitely take the white jersey to Paris tomorrow.
15:18 - Last year's winner, Cadel Evans, is on course. How much a year changes: 12 months ago, this was really a race of truth for the Australian, who had to overturn Andy Schleck's lead. Now he's riding to try and break into the top five.
53km - Rein Taaramae has finished. It's the fourth-best time for the Estonian youngster, one minute slower than Sanchez.
30km - Peter Velits (Omega Pharma-Quick Step) of was one second slower than Sanchez at the first check but has crossed the second check in third place, 18 seconds adrift.
15:14 - BMC team-mates Cadel Evans and Tejay Van Garderen chat in the start zone. Haimar Zubeldia of RadioShack starts now: he was in the top five but cracked on the final day in the Pyrenees.
15:12 - Peloton Mr Popular Pierre Rolland rolls down the ramp. He's eighth at the moment and finished tenth last year. Will he improve on his 2011 finish or will he crack and drop out of the top ten?
15:09 - Down rolls Janez Brajkovic of Astana, who has his eyes on Pierre Rolland's eighth place. The Slovenian crashed yesterday but he's a solid time triallist and should, you'd think, move above Rolland today. He trails the Frenchman by 43 seconds but took more than three minutes from him in the first ITT in Besancon.
15:07 - We're into the top ten as Thibaut Pinot, the stage eight winner, gets under way. Peter Sagan has just crossed the line, 3:44 down on the leader Sanchez.
15:04 - Nico Roche is down the ramp. The Irishman is currently 11th and is aiming for a top ten finish. It will be tough because 12th place Andreas Kloden is keen on that too. 10th place Thibaut Pinot will find it hard to hold onto that place because he's not so strong in ITT.
14:51 - Both Bradley Wiggins and Chris Froome are listening to iPods on the rollers preparing for their effort. Denis Menchov is the next rider to leave as we enter the top 15. They now leave at three-minute intervals.
14:43 - Stage 17 winner Alejandro Valverde is on course now as we enter the top 20.
14:32 - We're onto the top 25 riders now as Ivan Basso rolls down the ramp for Liquigas.
14:30 - No spotted shorts for Thomas Voeckler today: the French polka dot jersey has gone for a straight red pair. The Europcar rider is down the ramp now - he has a massive smile on his face because the crowds are goign crazy, chanting his name, cheering and clapping.
14:23 - We just spoke to Luis Leon Sanchez after his ride: "I'm getting good towards the end of the Tour, which is good because the team has lost so many riders. I had a hand injury but my team-mates have supported me well and I got a stage win too. The favourite today is Wiggins, he won the other time trial and I'm sure he'll be motivated to win again today."
14:18 - A poignant sight: Alexandre Vinokourov (Astana) rolls down a Tour de France ITT ramp for the last time in his career. The veteran Kazakh is retiring at the end of the season - this time for good.
53km - Gretsch's time at the top is over as Luis Leon Sanchez crosses the line a huge 37 seconds faster than the German. Rabobank's Sanchez, winner of stage 14 in Foix, has set the new target time of 1:06:03. That's a superb effort from the Spanish time trial champion, whose Tour got off to the worse possible start when he almost broke his wrist on stage one.
14:09 - We spoke to Patrick Gretsch, the current leader, after his effort: "It was a nice time trial. I knew that I could do really well. It's nice to still be in the lead. I did the best I could. Hopefully I'll be in the top ten tonight with that time."
14:04 - Yaroslav Popovych just finished the time trial 2:40 down on Gretsch in 13th place. The Ukrainian told us: "I think Wiggins is the favourite today. And he's a worthy winner of the Tour de France."
13:56 - Green jersey Peter Sagan has just gone down the ramp. For those who have just tuned in, yellow jersey Brad Wiggins is not on course until 3:33pm UK time.
53km - Vasili Kiryienka has set the second fastest time at the finish, 18 seconds behind current leader Gretsch.
30km - Spanish time trial champion Luis Leon Sanchez, all in red with a gold helmet, has set the fastest time at the second check. He's 16 seconds ahead of Gretsch with a new target time of 37:39 at the 30.5km check.
13:54 - The talk in the French media today surrounded Mark Cavendish's imminent departure from Team Sky. It is suggested that Cav will not continue playing second-fiddle in a team based around delivering grand tour success for either Wiggins and Froome. The world champion has been linked with moves to Omega Pharma-Quick Step and Saxo Bank. Report: Cavendish coy about Sky departure rumours
13:38 - Team Sky's Edvald Boasson Hagen is on course now - he's wearing the regular black Sky kit and not his Norwegian national road champion colours, this being the time trial.
14km - We have a new leader at the first intermediate check: Spaniard Luis Leon Sanchez, the stage 14 winner and national time trial champion, has over-taken Gretsch at the 14km mark. The Rabobank rider has set a new target time of 17:27, that's three seconds faster than the German.
53km - Britain's David Millar (Garmin-Sharp) didn't have a very good day: the stage 12 winner finished a huge 3:54 down on Gretsch's target time.
13:23 - Moments after switching bidon fetching for stage winning, Mark Cavendish compared his role in this year's Tour de France as akin to playing Wayne Rooney in defence. Despite admitting to taking pride in remoulding himself as a Cat.1 mountain pace-setter and water-carrier extraordinaire, Cavendish told reporters: "But I'm a sprinter - it's kind of like putting Wayne Rooney in defence. You know, I was kind of lost." Blazin' Saddles blog: Wayne Rooney on wheels
13:20 - It's sunny but cloudy in Chartres today, with a temperature of 20 degrees celsius. Pretty much ideal conditions for the stage. Chartres weather forecast
13:15 - 23-year-old American Tejay van Garderen (BMC) will certainly wear the white jersey as best young rider into Paris. He leads Thibaut Pinot (FDJ) by 3:16 in the standings and the Frenchman is no time trial specialist. Van Garderen is actually fifth in the GC - one place ahead of team-mate and defending champion Cadel Evans. Youth standings
53km - David Zabriskie has completed the course with the second best time, 44 seconds slower than Gretsch's target time.
13:00 - Thomas Voeckler milked his status as the 2012 Tour king of the mountains yesterday, wearing full polka dots as well as a polka dot Colnago bike frame and a red spot helmet. The Frenchman has an 11-point lead over Sweden's Frederick Kessiakoff. But unlike his team-mate Anthony Charteau, a surprise winner of the 2010 polka dot jersey, Voeckler is a worthy winner, having crossed 11 peaks in pole position and winning two mountain stages. Polka dot jersey standings
12:55 - Last year, of course, it was still all to play for entering the final time trial: Cadel Evans left it late to overturn Andy Schleck's advantage and take the yellow jersey on the eve of the race's final stage. Such has been Team Sky's domination, it's bit of a parade this year - no one can realistically overturn Wiggins or Froome at the top. Even if they both crash twice and puncture four times: the winner of the 2012 Tour will be a Briton.
53km - It's an Argos one-two at the top currently, with Matthieu Sprick setting the second fastest time at the finish, 52 seconds slower than compatriot and team-mate Gretsch.
12:45 - Let's have a run throught the other jerseys. Peter Sagan's third-place finish yesterday further increased his massive lead in the points classification: the Slovak youngster - a triple winner in his debut stage - is 124 points ahead of nearest rival Andre Greipel of Germany. Green jersey standings
12:40 - Germany's Patrick Gretsch, a former U23 ITT national champion, still leads at both checks and the finish. The Argos-Shimano rider's target time at Chartres remains 1:06:41.
12:35 - Rolland may drop to 9th in the GC then - but that would be a one-place improvement from his ride last year. Elsewhere, Andreas Kloden - currently 12th place - could squeeze into the top ten. He has 2:19 to make up on 10th place Thibaut Pinot, but the young Frenchman is not the best rider against the clock, whereas the RadioShack veteran is pretty solid. Nicolas Roche is 11th place, but he also is not so strong against the clock.
12:30 - The top five looks pretty much set in stone ahead of tomorrow's final stage to Paris, with no positions likely to change even after today's long ride. It's a bit closer towards the bottom of the top ten, with Frenchman Pierre Rolland currently eighth, but just 43 seconds ahead of Slovenia's Janez Brajkovic, who is quite an accomplished ITT rider. In fact, Brajkovic was 3:08 quicker than Rolland in the 41.5km ITT in Besancon.
12:25 - So, who are the favourite for today? Well, with Fabian Cancellara and Tony Martin - the two best time triallists in the world - absent, you'd have to say it was a two-way battle between the Tour's two top riders, Brad Wiggins and Chris Froome. White jersey Tejay van Garderen of BMC may contest the two Team Sky riders, although it's unlikely.
12:20 - Readers on their PCs, laptops, Macs, iPads etc can follow the live timing and splits in the graphic above these comments. For those on mobile devices, we'll bring you commentary, quotes and information throughout the afternoon - and then full coverage of the top 20 riders.
53km - Patrick Gretsch has now completed the time trial and, as expected, the German has set the best time so far: one hour, six minutes and 41 seconds. That's a huge 2:43 faster than second-place Johan Van Summeren of Garmin.
53km - The first rider has completed the course. The Lanterne Rouge Jimmy Engoulvent (Saur-Sojasun) comes home in a time of 1:12:49.
30km - Gretsch's time for the second check at Bailleau-le-Pin after 30.5km is 37:55. The second best time is Anthony Roux (FDJ), one minute and six seconds slower.
14km - Germany's Patrick Gretsch (Argos-Shimano) set a time of 17:30 at the first check in Mezieres-au-Perche. He has a 12-second advantage over American David Zabriskie (Garmin-Sharp).
12:12 - We pick up the live commentary just as Australian veteran Stuart O'Grady (GreenEdge) is about to start. 58 riders are currently on the road with 95 still yet to start. No one has completed the course as yet, but the early target time at both checks has been set by Patrick Gretsch of Argos-Shimano.
12:10 - It's a flat 53.5km course from Bonneval to Chartres, with intermediate checks at 14km and 30.5km.
12:05 - Wiggins is the last rider to start today's time trial: he'll head down the ramp at 3:33pm. The top 15 leave at three minute intervals, starting with Denis Menchov at 2:52pm. Before that, the riders leave at two-minute intervals. These times are UK time.
12:00 - Cavendish took the win after a brilliant lead out by his team-mate, the yellow jersey Bradley Wiggins. Today should be Wiggins's day - he is overwhelming favourite to repeat his success from the last ITT and take a second stage win. Wiggins is on the brink of becoming the first Briton to win the Tour de France, and it will be an historic one-two, with team-mate Chris Froome in second place, 2:05 down. Vincenzo Nibali completes the podium at 2:41. General Classification
11:55 - Yesterday, Mark Cavendish reminded the world of his supreme sprinting skills with a perfectly executed win ahead of Matt Goss in stage 18 of the Tour de France. Team Sky's world champion surged down the closing straight in Brive-la-Gaillarde to win the 222.5km stage ahead of Matt Goss (Orica-GreenEdge) and the green jersey Peter Sagan (Liquigas). Report: Cavendish back with a bang to win stage 18
11:50 - Welcome to live comments of the 53.5km individual time trial from Bonneval to Chartres, the penultimate stage of this year's Tour de France.