Gavin, who in November became the first British amateur ever to win a world title, has been withdrawn by GB head coach Terry Edwards who said the fighter's losing battle to make the 60kgs lightweight limit could have left him dangerously dehydrated.

The fighter was said to have flown home from the British training camp in Macau just 24 hours before the Games' opening ceremony.

"It was the toughest call I've ever had to make," Edwards, 64, said. "Frankie was obviously very disappointed and, yes, there were some tears.

"In the end it was my call and he didn't argue with the decision. I didn't want him to suffer any ill-health. I wouldn't be able to live with myself if that had happened."

The Birmingham boxer's feat of becoming the first Briton to win a world championship gold at Chicago last November had fuelled expectations that he could go one better in the weight division in which Amir Khan won a silver medal at Athens four years ago.

His shock exit even before a punch has been thrown will be seen as a major blow for the British Olympic Association who had viewed Gavin as a standard-bearer for the sport.

As a gold medal prospect Gavin would have received around £150,000 in training and living expenses from UK Sport over the last two years.

And the Amateur Boxing Association had hoped that a Beijing victory would have lifted the profile of a sport which is showing signs of a revival following Amir Khan's silver medal at Athens four years ago.

Edwards rejected criticism from former world champion Richie Woodhall that more could have been done to safely reduce Gavin's weight in the run-up to the Games. "He needed to shed another 3lbs but that proved too much," he said.

"He was dead at the weight although he'd given it 110 per cent. In this sort of climate it would have been dangerous to let him box."

The dangers of weight draining have been acknowledged ever since Fred Archer, the leading flat race jockey of the Victorian era, shot himself having become depressed at the strains of constant wasting.

Making the weight is what boxers regularly cite as the toughest aspect of the sport.