The 19-year-old, who joined Hull KR's academy at the beginning of the 2000 season, is the youngest-ever player to make his first-team debut for the Robins.

Saints coach Ian Millward said: "I am thrilled that we have signed an exciting Great Britain representative junior player.

"Jon picked the Saints over many other clubs and we see him as a long-term Super League player."

Wilkin has made 25 appearances for Hull KR this season, scoring seven tries and a drop goal.

Meanwhile, St Helens are talking to Australian winger Darren Albert about a new contract.

The former Newcastle Knights flier, who is the club's only ever-present this season, has 12 months left on his current deal but the club are keen to secure him long term.

He has scored 24 tries in his 31 matches so far this year.