Williams won the World Championship on Monday night, beating John Higgins 18-16 in a thrilling final in Sheffield.
The drama was relentless and after Higgins drew level at 15-15 there was an unexpected shift in momentum.
Williams reeled off two frames in a row, the second with a 100 break, but then missed a pink in the next frame that was match ball.
Higgins cleared with a run of 65, taking the frame, but Williams was not to be denied glory.
And Williams - who had the previous day promised to stick to his word and complete his press duties without the customary waistcoat (or little else, for that matter) - walked into the press conference after his win with just a towel on.
The snooker star then shed the towel, and looked mortified as the world's press looked on in laughter.
Moments before, Williams had said of his win: "It's unbelievable. Twelve months ago I wasn't even here. I watched it in a caravan.
"To play John in a final is an experience in itself.
"You've got to expect a comeback because when you're 50 or 60 in front he's the best I've ever seen at clearing up and that includes O'Sullivan.
"I was thinking, 'Jesus I'm not going to get over the line here'.
"I knew at the end if I didn't get enough he was going to clear up again.
"But I'm over the moon."
Additional reporting by the Press Association.