* Australian victorious in opening time trial
* That's a huge goal achieved, says Dennis
By Martyn Herman
UTRECHT, Netherlands, July 4 (Reuters) - Australian Rohan Dennis proved too hot to handle as the Tour de France began with a record-breaking 13.8-km individual time trial through the sweltering streets of Utrecht on Saturday.
The 38th of the 198 competitors to roll down the start ramp, the BMC Racing Team rider averaged 55.446 kph as he blasted round the cycle-mad city in 14 minutes 56 seconds.
He then had to stew in the hot seat as rider after rider failed to match his searing pace in suffocating temperatures more typical of his native Adelaide.
Dennis completed his white-knuckle ride in the highest average speed for a Tour de France individual time trial since Briton Chris Boardman's effort over 7-km in Lille in 1994, and it gave him ownership of the coveted yellow jersey for a day at least.
"It was a huge relief and a huge goal finally achieved," said Dennis who was five seconds quicker than second-placed German Tony Martin and six clear of pre-stage favourite Fabian Cancellara of Switzerland.
"So few people have actually won the yellow jersey, it's a huge honour," the Australian told reporters. "It was stressful waiting. I was shaking watching them come in one by one. There were a few close moments for sure.
"When Cancellara didn't beat me I finally could start to relax a bit."
An estimated 700,000 people turned out to watch as the Dutch 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 was enjoying his moment in the sun, the main contenders to wear the yellow jersey after the finale in Paris on July 26 avoided mishaps as they jostled for position ahead of what could be an incident-packed first nine days in northern France, with cobbles and uphill finishes in store.
Defending champion Vincenzo Nibali, whose Astana team caused controversy by allowing Lars Boom to start despite him returning low cortisol levels in an anti-doping test, finished 43 seconds back in 22nd place.
IMPRESSIVE PINOT
Britain's Chris Froome (Team Sky) was 50 seconds off the pace while Spain's Alberto Contador, striving to complete the first Giro d'Italia-Tour double since Marco Pantani in 1998, was 58 seconds adrift.
Thibaut Pinot, France's best hope for overall glory, was an impressive 18th.
The feelgood story of the stage was the debut of MTN Qhubeka, the first true African team to start the Tour.
Daniel Teklehaimanot, representing Eritrea and the first black African to compete in the race, had the honour of being the first down the ramp.
While he did not feature high in the standings, the team did celebrate a 10th-placed finish for Briton Steve Cummings.
Dennis, team mate of the more fancied general classification contender, American Tejay Van Garderen, will defend the yellow jersey on Sunday's flat 166-km charge towards Zelande on the Dutch coast.
"My long-term goal is to win one of the grand tours," Dennis said. "I'm one step in the right direction." (Editing by Tony Jimenez)