BRITAIN'S chances of Olympic road race glory ended as Greg van Avermaet of Belgium won gold.

Geraint Thomas had been among a chase group with a chance of a medal at Copacabana, but tumbled to the road on the concluding descent with 10 kilometres to go of the 237.5km race.

He apparently slid into deep concrete drainage on the left side of the road, but picked himself up to finish 11th. He did not require hospital treatment.

Thomas was in medal contention until his spill as - for the second straight Olympics, after Mark Cavendish's 29th-placed finish on The Mall behind Alexandre Vinokourov four years ago - Britain experienced disappointment on the road on the opening day.

Chris Froome was 12th and Ireland's Dan Martin 13th, while Bury's Adam Yates was 15th.

British coach Rod Ellingworth said: "Looking at Geraint there he was proper, proper disappointed. He knew that was a proper gold medal chance.

"He's all right. He's fallen heavy, he's got plenty of skin off, but he's okay, I think.

"I knew from the test event that descent was going to perhaps be a deciding factor in the race. And it was.

"When you think about how many riders crashed round there it was pretty mad really."

It was something of a phony war along the beautiful, but brutal, Rio coastline before the final full loop of the Vista Chinesa Circuit.

There the challenge really set in as 63 of the 144 starters finished.

Nibali and his Italy team-mate Fabio Aru increased the pace on the descent, knowing there was one more climbing section to come.

Yates and Thomas bridged the gap to join the Italians in an 11-rider group.

Thomas followed Nibali at the start of the final ascent as Yates lost contact.

Yates tried to help his leader behind, but Froome had to forge on alone with around 20km to go as Britain's chances dwindled.

Thomas could not follow Nibali, who was joined by Sergio Henao of Colombia and Poland's Majka.

Demon descender Nibali tumbled on the final downhill, taking Henao with him, allowing Majka to go alone.

Thomas also fell and with him went British hopes of a medal.

"Until we hit the final circuit they rode the perfect race," Ellingworth said.

"The way the lads wanted to race is how they actually raced. Just unfortunate about the crash at the end."