Rohan Dennis during yesterday’s time trial in Utrecht.

Australian Rohan Dennis proved too hot to handle as the Tour de France began with a 13.8-kilometre individual time trial through the sweltering streets of Utrecht yesterday.

One of the early starters in the 198-strong field, the BMC Racing Team rider averaged 55.446 kmh to stop the clock in 14 minutes 56 seconds to take the yellow jersey.

Germany’s Tony Martin (Etixx-Quick Step) was second quickest, five seconds behind, with Swiss Fabian Cancellara, one of the favourites, a second further adrift.

Dennis’s searing pace was the fastest average speed ever recorded in a Tour individual time trial – surpassing Briton Chris Boardman’s 1994 effort over 7km in Lille.

“I didn’t expect to go that fast. I was targeting around 16 minutes,” Dennis, who once held the hour record, said as he watched to see if anyone could beat his time.

An estimated 700,000 people turned out to watch the opening stage as the Netherlands welcomed the Grand Depart for the sixth time, and they were not disappointed as the sport’s powerhouses lit the blue touchpaper for the battles ahead.

While Dennis became the first Australian to win the opening stage of the Tour since Bradley McGee in 2003, the main contenders to be wearing the yellow jersey when it ends in Paris on July 26 avoided any mishaps on the high-speed curves.

Defending champion Vincenzo Nibali was 43 seconds slower than Dennis, Britain’s Chris Froome was 50 seconds back and Spain’s Alberto Contador was 58 adrift.

Today’s second stage sees the 198 riders embark on the 166km route from Utrecht to Zelande.

A sprint finish is expected, unless cross winds split the peloton, with Mark Cavendish bidding to add to his 25 Tour stage wins.

Meanwhile, Dutchman Lars Boom started the Tour despite showing low levels of cortisol in a test on the eve of the race.

Low levels of the hormone can be explained by the use of corticoids, anti-inflammatory drugs that are allowed out of competition but forbidden while racing unless a rider is granted a Therapeutic Use Exemption (TUE).

Boom had an outside chance of victory in the 13.8-km time trial but eventually finished 23rd, 44 seconds behind Dennis.

“I did not have the best preparation,” Astana rider Boom told re-porters.

Astana, the team of Nibali, are members of the MPCC (Movement for Credible Cycling) that applies stricter rules than the International Cycling Union (UCI) and the World Anti-Doping Agency (WADA).

Under MPCC rules Boom should have rested for eight days but UCI regulations, by contrast, do not forbid him from racing.

UCI president Brian Cookson said the rider had not broken any anti-doping rule.

“No rules of the UCI and the World Anti-Doping Agency have been broken so he’s allowed to ride the Tour de France,” Cookson said.

“No anti-doping rules have been broken in this case. Low cortisol levels in themselves are not proof of an anti-doping violation.”