Former England and Great Britain rugby league scrum-half Sean Long is to join Harlequins as assistant coach.
The 42-year-old is to leave a similar role with Super League leaders St Helens to help coach Quins’ attack.
Long won every major honour in his rugby league career.
“I have been looking at adding a coach to assist with some of the finer detail around running lines and creating numerical advantages for some time,” said Quins head of rugby Paul Gustard.
“I am delighted that Sean has decided to join Quins ahead of other Premiership options as he takes his first foray into coaching union,” he told the club website.
“We can see with the performance of St Helens this year the impact he is now having as a coach with their attack as they compete at the top of Super League and enter into the semi-finals of the Challenge Cup after a 40-point thrashing over Wakefield.”
Long won five Challenge Cups, four Super League Grand finals and two World Club titles during 12 years at Saints, and also played six times for England and 15 times for Great Britain.
He joins a Harlequins side who missed out on the Premiership play-offs by the narrowest of margins last month after James Lang’s last-second penalty miss saw them lose at Wasps and fail to overtake Northampton for fourth place.
“It’s time for me to pursue a new challenge and Quins is a top club with a group of talented players and hard-working staff; I can’t wait to join up with them,” Long said.
“I wanted to take this opportunity to thank everyone in rugby league for the time I have had there, but now I’m focused on Harlequins and am looking forward to getting started on the preparations for next season.”
Long, who leaves Saints immediately and will join up with Harlequins on 8 July when pre-season starts, began his coaching career with Hull FC after leaving Saints in 2009.
He then coached at Wigan, Salford and the Samoa national team before returning to St Helens as an assistant coach in 2014.
“He is a legend of this club and everyone loves him,” St Helens head coach Justin Holbrook told the Saints website.
“We are naturally disappointed to be losing such an influential figure at St Helens, but I wish him all the best for his next adventure at Harlequins.”