15:30 - Top five: 1. Tony Martin 58:38.76, 2. Phinney +5.37, 3. Kiryienka +1:44.99, 4. Van Garderen +1:49.37, 5. Kessiakoff +1:50.37.
15:24 - Contador crosses the line to set the ninth best time, 2:30 down on winner Tony Martin, who is lying prone on the ground - a mixture of tears and smiles.
46km - Tony Martin of German retains his world championships time trial title by just 5.37 seconds!
15:22 - One kilometre to go for Tony Martin... has he done enough to retain his rainbow jersey?
15:20 - Tony Martin looks very tired as he comes out of the final climb. He's being pursued by Contador, who he passes 10km ago. The Spaniard looks in good nick now - but it's too little too late.
46km - Martin is approaching the Cauberg on the fast downhill section ahead of the final climb. At the finish, Kessiakoff can only takes the third best time. Taylor Phinney then zips over the finish to set the first sub-hour time: 58:44.13 for the American. It's certainly enough for silver, but can he win gold?
15:17 - Phinney is closing in on Kessiakoff on the flat run-in after the Cauberg.
46km - Vasil Kiryienka looks good for the bronze: Tejay van Garderen cannot topple him after the Cauberg and crosses the line 4.38 seconds down on the Belarusian.
38km - Top five at the third check at 38.4km: 1. Martin 48:56.02, 2. Phinney +8.66, 3. Gruzdev +1:14.85, 4. Kiryienka +1:22.50, 5. Van Garderen +1:33.32.
38km - Tony Martin goes through the third time check at 38.4km and he only has 8.66 seconds on Taylor Phinney: it's going to come down to the Cauberg!
15:12 - Sylvain Chavanel is approaching the finish - and it's only ninth place for the Frenchman. Meanwhile, Tejay van Garderen is on the Cauberg. He started strong, but has tapered off a little in this ITT.
15:10 - The three riders currently in the winners' enclosure are Kiryienka, Gruzdev and Jan Barta. They won't be there for much longer - although Kiryienka could hold on for bronze.
30km - Top five at the second time check after 29.7km: 1. Martin 38:30.59, 2. Phinney +13.26, 3. Gruzdev +49.43, 4. Kiryienka +54.98, 5. Pinotti +58.88. Terrible shame for Pinotti, who crashed soon after the second check and needed to withdraw.
15:05 - Martin catches Contador: he has more than two minutes on his Spanish rival and is on-song for gold.
30km - Martin crosses the second time check with a 13-second lead over Phinney. He's got Contador in his sights and the gold medal almost around his neck.
15:02 - Taylor Phinney makes it through the same offending bend without any problems. But further back the road, Tony Martin has Alberto Contador in his sights...
15:00 - Pinotti gets back on his bike but then pulls up. It appears he cannot grip the handlebars with his left hand. His coach, Paolo Bettini, goes to talk to him and then shakes his head towards the camera. It's a broken collarbone for Pinotti. Heartbreak there.
14:58 - CRASH: Marco Pinotti goes down hard on a tight left-hander. It was a case of going from wet road to dry road, plus crossing some white lines. The Italian was starting to speed up too, and was looking good.
38km - Dutch hope Lieuwe Westra passes through the third check well down on the leader, Gruzdev. It's two minutes and 21 seconds in arrears...
14:55 - Phinney is now meant to be riding five seconds quicker than Martin. The American almost collides with a piece of road furniture around a tight bend though - that was close.
14:50 - GPS timing says that Taylor Phinney is currently riding one second slower than Tony Martin. This is going to be a very close thing.
14km - Top five at the first check after 14.3km: 1. Phinney 19:18.36, 2. Martin +4.37, 3. Gruzdev +15.08, 4. Kiryienka +23.64, 5. Van Garderen +24.40.
14km - Tony Martin looks very focused as he approaches the summit of the first climb. He's well on course, just four seconds down on Phinney at the 14.3km mark.
14km - Alberto Contador is a long way off at the first check - a huge 40 seconds down in 15th spot. The question is whether or not this is tactical. Perhaps he's just exhausted after his exploits in the Vuelta.
14km - Super time for Taylor Phinney at the first check: the young American is 15 seconds up on Gruzdev and now has the target time after 14.3km.
38km - Janez Brajkovic is really suffering today: the Slovenian is well over two minutes down on Gruzdev at the third check. It's two seconds slower than Jakob Fuglsang. They're both having real stinkers.
14km - Frederik Kessiakoff of Sweden is 20.68 seconds down on Gruzdev at the first check so is clearly suffering a little today.
14:38 - Tony Martin really looks supreme in this early flat section of his race. That said, Alberto Contador looks rather composed too - although not as poetic as his German rival.
14km - Italy's Marco Pinotti struggled in the TTT for BMC. He's now approaching the first check after the first climb. He's 19.32 seconds down on Gruzdev, so it's going to be a big ask for the likable veteran to turn things around today.
14km - American Tejay van Garderen is on the opening climb. He's going well: 9.32 seconds down on Gruzdev at the first check.
46km - We have a new leader at the finish: Vasil Kiryienka of Belarus has a very strong final section to cross the line in a time of one hour, 23.75 seconds. The 31-year-old takes 11.45 seconds off Gruzdev's previous best time.
14km - Sylvain Chavanel is approaching the first check. The Frenchman is off the pace: 14.68 seconds behind Gruzdev after the first climb.
14:28 - Dmitriy Gruzdev is a little-known 26-year-old Kazakh rider who is a two-time national time trial champion but rarely rides any of the big races for his team Astana. Gruzdev still leads at each time check, and the finish.
46km - Britain's Alex Dowsett sets the provisional second-best time at the finish, crossing the line after a strong second half of his ride 29.62 seconds down on leader Dmitriy Gruzdev of Kazakhstan.
14:24 - Alberto Contador, the big favourite from Spain, is now on course. Just one more now: the defending champion, Tony Martin of Germany. Can he turn a disappointing season around - and double up after his Omega Pharma-QuickStep TTT gold last weekend?
38km - Kiryienka goes through the third check 7.65 seconds down on the leader Gruzdev.
14:22 - Taylor Phinney is down the ramp, so we're down to the last two now: Contador and Martin.
14:21 - There is still a lot of liquid on the road. The sun may be out at the start, and the rain may have ceased, but the water is still everywhere. It's hard because there are many different road surfaces - bricks, cobbles, flat stones and tarmac.
14:20 - Sean Kelly: "I would not like to go beyond Alberto Contador for the win today."
14:18 - Here's Frederik Kessiakoff of Sweden, one of the big outside favourites today. He won the ITT in the Vuelta last month and could pull something out of the bag today - although he said this morning that the course was not hilly enough for him.
14:15 - Ireland's Michael Hutchinson says that this course today is one that riders must attack with brains, not going all-out too early. "Whoever wins it will be very strong in the second half," he said. "I'd be pretty confident to wager that they won't have the quickest time over the first and second checks."
30km - Vasil Kiryienka of Belorussia has set the second best time at both the first and second check. He's just 5.55 seconds down on Gruzdev at the second check.
14:12 - Janez Brajkovic and Luke Durbridge are both on course now as the sun starts to shine again.
14:10 - Ireland's Michael Hutchinson just told David Harmon and Sean Kelly in the commentary box that he expects Alberto Contador to win the ITT today.
46km - Kazakhstan's Dmitriy Gruzdev keeps his momentum going to post the best time at the finish, just over a minute ahead of previous leader Zoidl of Austria. Gruzdev completed the 45.7km course in a time of one hour, 35.20 seconds.
14:08 - Ireland's Michael Hutchinson is in the Eurosport studio after his ride. He is currently 3:26.42 down in ninth place. "It's tough because there's a lot of headwind and the headwind coincides with the climbs. The descents are so short so you don't have a chance to relax. Whoever wins this one will really deserve it because it's really hard out there."
14:05 - Dutch favourite Lieuwe Westra is down the ramp, followed by Germany's Bert Grabsch.
38km - Dmitriy Gruzdev has the best time at the third check after 38.4km. The Kazakh was more than a minute ahead of any of his rivals and is now approaching the finish. He should be in the provisional lead soon.
14:00 - Sweden's Gustav Larsson, popular with the locals because of his ties with Vacansoleil-DCM, is down the ramp. The road is drying out in Heelen, but the cobbles and flag stones will still be slippery. Spain's Jonathan Castroviejo is next - he wore the first red jersey of the Vuelta last month after crossing the line for Movistar first in the opening TTT.
13:55 - Australia's Cameron Meyer is down the ramp, two minutes after Jeremy Roy of France gets his race-against-the-clock underway.
46km - The first ten riders have completed the course: the current leader is that man Riccardo Zoidl of Austria, who crossed the line with a time of 1:01.36.03 - more than a minute ahead of Carlos Oyarzun in second place.
14km - The second Dutch rider in this time trial, Wilco Keldeman, is currently on the first climb of the day, the Sint Remigiusstraat. The fans are cheering him on, but it's a slow time at the first check: 31.61 seconds down on the current leader, Dmitriy Gruzdev. The rain is very localised - it's pouring down on Keldeman but it has cleared at the start.
14km - Rein Taaramae is not going well either: the Estonian is 47.32 seconds down at the first check.
46km - We have five riders in the finish zone now. The current best time at the finish has been set by the Chilean rider Carlos Oyarzun, who completed the 45.7km course in a time of one hour, two minutes and 42.19 seconds.
14km - Thomas de Gendt is not going very well: the Belgian is currently 23.36 seconds down in fifth place at the first check. He suffered from that huge downpour just after he started.
38km - Riccardo Zoidl is quickest at the third time check at 38.4km. The Austrian posts a time of 51:15.03 - almost one minute quicker than second place Jay Robert Thomson of South Africa.
14km - We have a new leader at the first check: Dmitriy Gruzdev of Kazakhstan rides through the 14.3km mark 12.70 seconds faster than previous leader, Riccardo Zoidl of Austria.
13:35 - The rain has stopped and the sun is back out again as Vladimir Gusev of Russia rolls down teh ramp. The big question is whether or not the course will dry out before the big guns...
30km - As he was at the first check, Austria's Riccardo Zoidl was quickest at the second check after 29.7km. His target time is 39:59.89 - a full 51.82 seconds quicker than the current second-best rider, Matej Jurco of Slovakia.
13:25 - With Olympic time trial champion Bradley Wiggins and his Sky team-mate Chris Froome both sitting out this one, Britain's only hope comes with Alex Dowsett.
13:25 - Rein Taaramae (Estonia), Thomas de Gendt (Belgium) and Alex Dowsett (Britain) are all on course now. De Gendt finished third in the Giro in May and was an attacking force in the Vuelta after a disappointing start. He could well be an outsider today - although it the rain clears for the later runners, he'll certainly be at a disadvantage.
13:20 - The rain is really pouring now in Limburg - this will make things very unpredictable. The first five riders have passed through the second intermediate check with Chile's Carlos Oyarzun setting the best time so far of 41:06.28. He's 14.47 seconds faster than the second-best rider, Norway's Reidar Bohlin. Both of them are more than two-and-a-half minutes ahead of the other three to come through.
13:15 - There's been some drizzle and then light rain at the start, making the ramp pretty slippery. The organisers are currently wiping it down to avoid any spills.
14km - The first ten riders have now come through the first check point at the 14km mark. The leader was the last rider to pass through, Austria's Riccardo Zoidl, who has set the target time of 19:46.14 after 14km and ahead of the first climb - that's 25.78 seconds quicker than second-placed Matej Jurco of Slovakia.
13:05 - Other names to throw into the ring (perhaps for bronze, should this race keep to the script) are Sweden's Frederik Kessiakoff (who won a simular ITT on the Vuelta), American pair Tejay van Garderen and Taylor Phinney, Belgian Thomas de Gendt, France's Sylvain Chavanel, Swede Gustav Larsson and his Vacansoleil-DCM team-mate and Dutch home favourite Lieuwe Westra, Italy's Marco Pinotti and the Australian Cameron Meyer.
13:00 - Compared to last year's fast route around Copenhagen, this Limburg course is very demanding. There are three climbs on the hilly course: Sint Remigiusstraat (1km at 7.7% after 16km), Rozekoel/Bundersberg (800m at 5.4% after 39km) and the Cauberg (1.2km at 5.8% after 43km). The final climb and the long flat drag to the finish will be key - as it was in the men's team time trial where Martin's team OPQS kept it together to beat the fractured BMC of Phinney and van Garderen.
12:55 - It's sunny, with a light cloud covering, but fresh in Valkenburg - with temperatures in the mid-teens and a gusting wind of 20-25km/h from the west. This could create a testing headwind going up the Cauberg towards the finish... Full Yahoo! weather report for Valkenburg
12:52 - For many, this is a two-way battle between Contador and Martin. The hilly course should favour the Spaniard, although he will be fatigued by his winning ride in the Vuelta, and he has admitted fears of how he well will ride a time trial outside the framework of a Grand Tour. Martin has had terrible luck in time trials this years with punctures. He also saw both his Tour and Vuelta hampered by a fractured wrist. The German did, however, take silver in the Olympics ITT.
12:50 - Key start times to note: 14:54 - Cameron Meyer (Australia), 14:00 - Gustav Larsson (Sweden), 14:02 - Jonathan Castroviejo (Spain), 14:08 - Luke Durbridge (Australia), 14:10 - Sylvain Chavanel (France), 14:12 - Svein Tuft (Canada), 14:14 - Tejay van Garderen (USA), 14:16 - Marco Pinotti (Italy), 14:18 - Frederik Kessiakoff (Sweden), 14:20 - Taylor Phinney (USA), 14:22 - Alberto Contador (Spain), 14:24 - Tony Martin (Germany).
12:45 - We have about eight riders on the road now and will be bringing you the split times as and when. The first big-name rider to leave will be Rein Taaramae of Estonia at 13:20 UK time. Others soon following will be Thomas de Gendt of Belgium (13:22), Alex Dowsett of Great Britain (13:24), Ramunas Navardauskas of Lithuania (13:42), Jakob Fuglsang of Denmark (13:44), Janez Brajkovic of Slovenia (13:46) and Patrick Gretsch of Germany (13:48).
12:30 - Ecuador's Segundo Navarrete gets the 2012 World Championships team time trial underway, rolling down the ramp in the start town of Heerlen..
12:25 - There are 58 riders on the startlist: Ecuador's Segundo Navarrete gets things under way at 12:30 UK time, with riders leaving at two-minute intervals right though to defending champion Tony Martin of German, who will roll down the ramp at 14:24 UK time.
12:25 - It's an undulating course in the Netherlands with three categorised climbs, including the final ascent of the Cauberg - which is used in the annual Amstel Gold spring classic and was also used in the men's team time trial last weekend.
12:20 - Welcome to live coverage of the World Championships elite men's time trial from Limburg, where Germany's Tony Martin will defend his rainbow jersey over a 45.7km technical course in the Netherlands.