Twelve months ago the 43-year-old – twice a world champion – was sliding down the rankings and came close to quitting the sport after failing even to reach the Crucible, losing to Grimsby’s Stuart Carrington in the qualifiers.
It was only wife Joanne who persuaded the former world No 1 to carry on playing.
The Welshman changed his technique and training routine, enjoying a renaissance season as he won the Northern Ireland Open and German Masters.
And on Monday night he capped a remarkable campaign, beating John Higgins 18-16 in Sheffield to bank £425,000 and his third world title.
But Williams had to withstand a ferocious challenge from Higgins, seeing his 14-7 lead disappear to be tied at 15-15 before holding his nerve to lift the famous trophy.
“It’s unbelievable,” said Williams. “Last year I wasn’t even here. Last year I watched this in a caravan having some beers. I just can’t believe it.
“Last year I was seriously thinking of giving up, she (wife Joanne) said I can’t sleep in the house 24 hours a day.”
Victory made Williams the oldest champion since 45-year-old Ray Reardon in 1978.
It also created history being the longest gap between world titles having last triumphed, aged 28, at the Crucible 15 years ago.
How the sporting landscape has changed since 2003: David Beckham swapped Manchester United for Real Madrid, Roger Federer won his first grand slam title and Johnny Wilkinson kicked England’s rugby union team to World Cup glory.
Plenty has changed for Williams in the intervening years – including the receding hairline and expanded young family – but the player they call the ‘Welsh Potting Machine’ still boasts a formidable array of shots.
In 2003 it was Ken Doherty who Williams beat in the final; yesterday it was another member of snooker’s royalty in Higgins.
For the 42-year-old – chasing a fifth Crucible title – it was more final heartache after losing in last year’s climax to Mark Selby.
Williams had raced into a 5-1 lead on Sunday, but Higgins battled back to level at 7-7.
However, the Welshman, who made his Crucible debut in 1997, won the final three frames before returning to the famous Sheffield theatre on Monday afternoon to take the opening four frames.
Williams – watched from the balcony by wife Joanne and sons Connor, Kian and Joel – was not scoring heavily with eye-catching centuries, but he was consistent.
He pounced after fluking the opening red with a 61 break, then created a 56, following two different plants, 69 and – after Higgins twice spurned good opportunities – Williams advanced with a 52 clearance.
Leading 14-7 at the afternoon interval, in their best-of-35 contest, there were even suggestions left-hander Williams could be crowned champion with a session to spare.
But Higgins – who has collected 30 ranking titles in a glittering career – is renowned in snooker as a player who refuses to admit defeat, and the obituaries were premature as he reeled off the next three frames.
Returning after the interval, Higgins missed the black off its spot, but for once Williams failed to punish him and the Scot drilled in a long-range red on his way to a 67 break, and finally end his seven-frame losing streak.
Then, after Williams faltered on 65, slapping the table in frustration after a missed blue, Higgins pinched frame 23 with a 72.
Already boasting the highest break over the previous 16 days, a 146, Higgins had a £50,000 147 maximum bonus in sight in the next frame. He pocketed 10 reds and 10 blacks, but stumbled on the 11th red.
But Williams took a five-frame advantage into the evening session after winning the initial safety battle and pouncing after Higgins failed to pocket a red along the cushion.
Needing to win 8-2 in last night’s session, Higgins produced a near-flawless five frames to level the match at 15-15.
He smashed in a 131 clearance and, when Williams broke down on breaks of 58 and 47, Higgins twice nipped in to pinch the frames with 67 and 82.
And the Scot held his nerve with a 47 score to claw back another frame before Williams again broke down on 47, leaving the door open once more for Higgins to sneak in with a 62 and level the match.
Williams could have been forgiven for fearing the worst when he allowed Higgins another chance – after faltering on 41 – but this time the Scot could not capitalise. It was the Welshman’s first frame of the evening,and he quickly followed that up, a break of 100 taking him to 17-15 and the edge of victory.
Williams thought he had victory in sight, but missed a title-winning pink on a 63 break, and Higgins nipped in with a 65 clearance. The Welshman was not to be denied. Holding his nerve with a 69 break to complete an amazing journey in 2018.
All that was left for Williams to do was to make good on a promise to do his post-final media conference naked.