Martin, who had made this race the focus of his season, made little attempt to get back up as he held his collar bone and waited for medical attention.

It was the most dramatic illustration of the huge role the weather played as the first Grand Tour of the season started under damp skies.

Orica GreenEdge took victory, gifting the leader's pink jersey to birthday boy Svein Tuft, and although they had been the favourites they could be grateful for being the second team out as they benefited from dry roads.

The rain soon began to fall, costing general classification hopefuls Nairo Quintana (Movistar) and Joaquim Rodriquez (Katusha) significant chunks of time against Nicolas Roche, whose Tinkoff-Saxo team held it together as the roads became more and more slippy, as well as late starters Rigoberto Uran and Cadel Evans.

The wet weather had not deterred thousands of fans from lining the Belfast roads, but the mood changed as the big screens showed Martin tumbling to the ground.

Garmin-Sharp manager Jonathan Vaughters reacted to the crash immediately on Twitter.

"So sad. Nothing to be done. Professional bike racing is cruel," he wrote.

Martin's uncle, 1987 Giro winner Stephen Roche, was also on Twitter moments after the crash.

"Absolutely gutted Dan @DanMartin86" he wrote.

Martin, a stage winner on last year's Tour de France and cousin of Nicolas Roche, was considered one of the contenders at the start of the race, but the crash left his team's plans in ruins.

They were able to get five riders to the line together - the minimum required in the team time trial - but they finished three and a half minutes down on Orica GreenEdge's time of 24 minutes 42 seconds, surely eliminating 2012 winner Ryder Hesjedal from contention too.

It was another huge slice of bad luck for Martin, who was on course to defend his title at Liege-Bastogne-Liege at the end of April before crashing on the final bend.

The roads began to dry late on, allowing Rigoberto Uran's Omega-Pharma Quick-Step team to take second place, just five seconds off Orica GreenEdge, to leave the former Team Sky rider - second in the Giro last year - as the best placed of the GC contenders, with BMC Racing's third place putting Cadel Evans just two seconds further back.

Tinkoff-Saxo wound up fourth, 23 seconds off the pace, to leave Nicolas Roche content.

"It was really tough," he said of the conditions. "Looking at the forecast we were hoping it was going to be okay but unfortunately not, but I think we set a good mark.

"I said if we only gave up 20-30 seconds from the lead team we'd be in good shape."

Ben Swift led Team Sky home in fifth, while Quintana's Movistar could only manage eighth, 55 seconds back, and Rodriguez found himself 93 seconds back after a disappointing run from Katusha.

But nobody could dampen the mood of Tuft as the Canadian celebrated his 37th birthday in pink.

"An amazing day," he said. "It's a pretty crazy way to spend your birthday but to finish on that note, what a treat. I can't thank my team-mates enough for giving me that opportunity. It's a once-in-a-lifetime thing, what a fantastic team.

"They gave me a great gift, it was really a birthday present. This team is really selfless in that way."