As he basked in his hero status, Phelps knocked back beers and shots of spirits. And when a student offered him the glass bong engraved with red writing, he did not hesitate, says our source.

The 6ft 4ins athlete, in a white T-shirt and navy cap worn back to front, clasped the device in his huge hands and inhaled deeply.

Our source said: "You could tell Michael had smoked before. He grabbed the bong and a lighter and knew exactly what to do.

"He looked just as natural with a bong in his hands as he does swimming in the pool. He was the gold medal winner of bong hits. Michael ended up getting a little paranoid, though, because before too long he looked like he was nervous and ran out of the place."