World number one snooker player Ronnie O'Sullivan beaten by amateur James Cahill

World number one Ronnie O'Sullivan has crashed out of the World Snooker Championship in the first round after losing to amateur James Cahill.

The result is one of the biggest shocks in the tournament's history, as O'Sullivan had been pursuing his sixth world title.

Cahill, the first amateur to qualify for the tournament, held his nerve to beat the five-time champion 10-8 at the Crucible.

O'Sullivan has suffered the defeat after a season which saw him win five titles and compile his 1,000th career century on his way to victory in the Tour Championship.

He had trailed 5-4 to Cahill on Monday but managed to bring the contest level to 8-8 on Tuesday.

O'Sullivan missed a great chance to snatch the 17th frame and Cahill took advantage to move 9-8 in front.

"The Rocket" looked on course to set up a final-frame decider only to inadvertently pot a red when breaking the pack open from the blue, leaving Cahill to produce a break of 53.

The 23-year-old from Blackpool will face Scotland's Stephen Maguire in the second round.

He became a professional in 2013 and his highest world ranking is 76.

O'Sullivan reportedly said he was not feeling well after he bowed out of the tournament in the first round for the first time since 2003.