Tom McCooey takes a look at 10 players who made the switch during their careers.
Laughton had played for Saints between 1963 and 67 before signing for Wigan for 4,000 in May 67. He made 180 appearances for Wigan, scoring 36 tries.
Iro won four Challenge Cups, two league titles, a Lancashire Cup, John Player Trophy and a Regal Trophy at Wigan. He signed for Saints in 1999 and played in their 2000 Grand Final win over Wigan.
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Platt signed for Wigan from St Helens in 1988, going on to make 199 appearances in a trophy-laden spell before leaving to sign for the new Auckland Warriors franchise in 1994.
Gary Connolly was sold to Wigan in 1993, having played for Saints since 1988, including in two Challenge Cup final defeats to the Cherry and Whites. But it was at Wigan where he became one of the best centres of all time.
Atcheson went on to make 62 appearances for Wigan, winning seven trophies in the process. After a stint at Oldham, he signed for Saints in 1997..
Goulding signed for Wigan in 1988 and despite an unsettled three-season spell at Wigan collected four winners medals from his 45 games. Moved to Saints in 1994.
Long only made 12 appearances for Wigan after signing from St Judes before being released by the Warriors in 1997. Moved to St Helens where he enjoyed a successful 12 years.
Bibey made 42 appearances for Wigan between 2001 and 2003.
After moving to Leigh, Bibey joined Saints for a short stint in 2004.
Higham joined Wigan for the 2006 season following a convoluted transfer to the Warriors from St Helens - via a swap deal with Bradford which saw Terry Newton join the Bulls.
Matty Smith joined Wigan from Salford in 2012 - having faced Wigan in St Helens colours in the 2010 Grand Final. Re-joined St Helens in 2017.