The boxing career of former dual world champion Steve Collins came to a surprising and abrupt end in a London gym on Monday afternoon when he collapsed face down on the canvas during a sparring session. He spent the night in hospital where he underwent tests. His trainer, Jimmy Tibbs, announced yesterday that Collins would not box again.

Collins went through a series of medical tests, including a brain scan, but was given the all clear yesterday and was discharged. He was preparing for a comeback fight against an unnamed opponent on the same card as the WBO super middleweight title fight between Joe Calzaghe and Rick Thornberry in Cardiff on June 5th.

Collins was by far the most successful Irish-born and Irish-based boxer in the history of the sport. He won the WBO middleweight title in controversial circumstances in Millstreet in Cork in March of 1995 against Chris Eubank and defended it successfully in a re-match in Pairc Ui Chaoimh subsequently.

He then accepted a challenge by the reigning British super middleweight champion, Nigel Benn, whom he beat on two occasions in Britain. In all, he made seven successful defences of his crown. He was due to defend against Calzaghe in Cardiff in 1997 but decided to retire undefeated, although he continued to hanker after a bout with the American, Roy Jones Jnr, but Jones would not grant it. Collins returned hoping that a challenge for Calzaghe's WBO super middleweight title might earn him a shot at Jones, who holds the WBC crown.

All those plans have now come to nought. Yesterday Tibbs, one of the most respected men in British boxing, said: "When Steve got himself together after the tests and he had been given the all clear, we all agreed that the best thing for him to do was to stop boxing.

"I was delighted when he told me that he wouldn't be boxing any more. He said he believed what had happened was a warning for him and he needed that to stop boxing.

"To see a tough guy like Steve collapsing on the canvas like that was frightening."

Collins could not be contacted yesterday afternoon but his promoters, Sports Network, confirmed that he was in good form and was being released from hospital.

Collins's wife, Gemma, flew to England last night and a press conference is being held at Cheshunt in Hertfordshire this morning at which he is expected to confirm his retirement. He is expected back in Dublin by the end of the week.