Rohan Dennis
Dennis will wear yellow going into stage two. Getty Images

Rohan Dennis produced a sizzling display to win the opening stage of the Tour de France in Utrecht as Chris Froome's hopes took an early blow.

The Australian had the honour of being zipped into the first leader's Yellow Jersey after he saw off favourite Tony Martin in the time trial.

But in the battle of the four main General Classification riders it was reigning champ Vincenzo Nibali who came out on top.

The Italian clocked 15 minutes 39 secs to finish seven secs ahead of Britain's 2013 winner Froome as riders struggled in the 91 degree heat.

Two-time champ Alberto Contador was 15 secs adrift of Nibali and Nairo Quintana lost 18 secs over the 8.57mile (13.8km) route.

The gap is only seconds with more than two thousand miles still to race but they could prove crucial in what is set to be one of the tightest Tours in years.

Dennis, who set the World Hour record in February before British duo Alex Dowsett then Sir Bradley Wiggins eclipsed his mark, is no slouch.

But he still was a surprise winner on the 39-turn course around the sun-scorched Dutch city after clocking 14 minutes 56 seconds.

Dennis, 25, was the 38th of the 198 riders sent on their way and he spent two hours in the hot-seat before being confirmed as the seventh Australia to wear Yellow.

The BMC rider's average time of 55.446kph beat the previous best set in a time trial of 55.152kph by Britain's Chris Boardman in Lille in 1994.

Three-time world time trial champion Martin got closest but the German, nicknamed 'The Tank', lacked the power this time and lost by five seconds.

The Etixx QuickStep rider admitted: "I'm very disappointed. I wanted to win and any other result is a bad one. I couldn't handle the heat."

But the 102nd Tour's Grand Depart, inevitably, was not without its drugs controversy with Nibali's Astana team again at the centre.

The Kazakh-team's Dutch rider, Lars Boom, failed a pre-Tour medical check after showing a low cortisol level.

Though it is not a doping offence, it can indicate drug use and Boom, 29, should have been withdrawn from racing for eight days as part of a voluntary code the team had signed up to.

Astana, decided that Boom would take to the start line after the world governing body, UCI, refused permission for him to be replaced.

Boom won the stage over the cobbles for his former team last year and will be a key figure with Nibali expected to attack on Tuesday's cobbled section.

The 2011 Tour of Britain winner also insisted he has done nothing wrong, telling Dutch television he had been ill after last month's Criterium Du Dauphine race in France.

Boom said: "I've been using a puffer for my asthma for 10 years. Maybe these things have an affect. I have always been 100per cent against doping. I have not done anything dodgy."