Ronnie O’Sullivan’s hopes of becomes snooker biggest ever prize winner are over for the time being after he suffered a shock defeat in the Northern Ireland Open.

Ronnie O’Sullivan. Picture by Monique Limbos

World number 82 Elliot Slessor produced the best performance of his career so far to record a famous win over the five-times world champion – beating him 4-1 in Belfast.

It means O’Sullivan, who won the English Open last month and last week’s Shanghai Masters, can no longer win the £1million bonus on offer by World Snooker.

The huge sum was on offer for any player who would win all four of this season’s Home Nations event – English Open, Northern Ireland Open, Scottish Open and Welsh Open.

But O’Sullivan’s defeat now blows the tournament wide open heading towards the last 16 stage. The winner of the event will lift the Alex Higgins trophy and take home a cheque for £70,000.

Following withdrawals and early exits, only two players in the world’s top 16 are currently left in the competition – John Higgins and Mark Williams.

But the day belongs to 23-year-old Slessor whose win will be remembered for the rest of his life.

Earlier this season he impressed the snooker world by reaching the quarter-finals of the Indian Open, beating Shaun Murphy along the way.

Meanwhile, a busy fourth day in the Northern Ireland Open saw defending champion Mark King also crash out after he lost 4-1 to the impressive 17-year-old Yan Bingtao from China.

Bingtao, who recently made the semi-finals of the International Championship, next faces Ryan Day in tonight’s last 16 clash.

There was also a surprise defeat for 2010 world champion Neil Robertson who lost 4-3 to Robert Milkins.

Neil Robertson. Picture courtesy of Monique Limbos

The defeat is a blow for the Australian as he is in desperate need for prize money in order to qualify for The Masters in January.

It means Robertson will need a good run in the upcoming UK Championship to have any chance of making the prestigious invitational event.