Ronnie O'Sullivan overcomes Matthew Stevens at Northern Ireland Open

Ronnie O'Sullivan played his trump card en route to the last 16 of the Northern Ireland Open in Milton Keynes.

The reigning world champion loudly broke wind early in the fourth frame of his match against Welshman Matthew Stevens, which he went on to win 4-2.

O'Sullivan appeared to apologise to Stevens before turning to embarrassed referee Ben Williams and joking: "Was that you?"

Later, O'Sullivan told Eurosport: "I dropped my guts – I am taking full ownership of that. I have had stomach problems for a couple of months.

"I did say 'Was that you' to the referee but I am proud of that one."

O'Sullivan was keen to avoid a stinker when he returned later on Thursday for his match against Thailand's Thepchaiya Un-Nooh.