Lyon is looking foward to the challenge of Super League

The 22-year-old was capped by the Kangaroos at 19 and has also featured for Parramatta in the Grand Final.

Saints coach Ian Millward said: "This is the biggest signing for St Helens since Mal Meninga. Jamie is already a world-class strike centre.

"This is a huge boost for the club and a clear sign of its intensions to remain the top league side in Britain."

Lyon, who has been pursued by a string of leading clubs both in Britain and Australia since deciding his future lay away from Parramatta earlier this year, said he was excited about the move.

We may have recently sold the best centre in England, but I feel that we have replaced him with the best in the world Eamonn McManus

"I am raring to play for the Saints, particularly as I will be linking up with Darren Albert, the quickest winger in the British game," he said.

"St Helens impressed me by their clear ambition to remain a leading world rugby force and they stood out from all the clubs which showed interest in me, even in Australia."

Meanwhile, Knowsley Road chairman Eamonn McManus believes the club have found the ideal replacement for Martin Gleeson, who moved to Warrington in July.

"We may have recently sold the best centre in England, but I feel that we have replaced him with the best in the world," he said.