Ronnie O'Sullivan shakes hands after his shock World Snooker Championships first round loss to 23-year-old amateur James Cahill ©Getty Images

Amateur player James Cahill pulled off the biggest shock in the history of the World Snooker Championships as he completed a 10-8 first-round win over five-time champion Ronnie O'Sullivan.

The world number one trailed 5-4 overnight at the Crucible Theatre in Sheffield  and and slipped 8-5 behind as he missed numerous simple chances against the 23-year-old qualifier.

A jaded-looking O'Sullivan then somehow found some form, scoring breaks of 104 and 89 to level.

But Cahill, who does not have a world ranking, moved decisively ahead once more.

"I could barely stand up at the end," the Blackpool potter told BBC Sport.

"I am not really sure what to say.

Five-times world champion Ronnie O'Sullivan contemplates a shock first-round exit at the World Championships ©Getty Images
Five-times world champion Ronnie O'Sullivan contemplates a shock first-round exit at the World Championships ©Getty Images

"I scored a good pressure 70 to go 6-5 up and after that I felt like he was the one under pressure.

“He didn't want to lose to me.

"I have always believed in myself and that I can beat anyone on my day. 

"I want to show what I can do now."

Earlier, 1997 world champion and BBC pundit Ken Doherty accused Ronnie O'Sullivan of playing with disrespect during Monday’s first session.

"He played very casually, it was almost with a lot of disrespect in a way," he said.

"He didn't want to be there, didn't look like he fancied the job.”

After O’Sullivan had been beaten, Doherty said he did not look well, which the former later confirmed.