And it augurs well for Wales’ November Test schedule – they face Tri Nations sides New Zealand, South Africa and Australia – that Williams remains in such blistering form.

“I had been finding it really difficult to get involved in games this season, but I felt sharp tonight,” he said.

“I just wanted a crack, to be honest. I feel pretty good.

“It was a very tough game and there was a lot of pressure on us to play well. It would have been doom and gloom in Wales had we lost.”

Williams’ scintillating score helped inflict only a second defeat of the season on Aviva Premiership leaders Irish.

And the visitors could have few complaints as Williams’ fellow Lions wing Tommy Bowe claimed an early touchdown before fly-half Dan Biggar kicked four penalties.

Centre James Hook, who moved to 10 when Biggar went off injured early in the second period, added a conversion and penalty, while Irish mustered a Sailosi Tagicakibau interception try, plus 11 points from Ryan Lamb.

The Ospreys, Heineken quarter-finalists in each of the past three seasons, delivered one of their finest European performances.

They were hungry from the start, and the win has put them firmly in quarter-final contention from Pool Three – a punishing group that also includes Irish heavyweights Munster and Jonny Wilkinson’s Toulon.

Irish head coach Toby Booth also paid tribute to Williams, claiming: “He came up with something exceptional – it was Shane Williams at his best.

“I am all for the entertainment business, and it was a great piece of skill by him. It’s what the Heineken Cup is about, and he has been doing that for a long time.”

Booth had no complaints about the result, adding: “We came second, and we deserved to come second.

“We didn’t have the ball in the first half, and we haven’t yet discovered a magic formula to win without the ball.

“We are disappointed with some of the things we produced tonight, but there is a lot of rugby left to be played in this pool. We have to be brutally honest, and we didn’t deserve to win the game.”

The Ospreys’ display underlined that they mean business in Europe this term, and assistant coach Jonathan Humphreys reflected on a job well done.

“We are pretty satisfied,” he said. “I thought we were smart, we were physical and we scored some nice tries.

“I always enjoy watching Shane play. It’s why he was named world player of the year. Some of the tries he scores are ridiculous, and hats off to him.

“We’ve got to go to Irish and Munster, so this group is going to be tough all the way, but we are pretty experienced now.”