Saints will make a piece of club history when they face Betfred Super League newcomers, Toronto Wolfpack, on Saturday, February 29 - the first-ever meeting between the two clubs.
But the Canadians 'home match' has also been switched to London's Allianz Park, which is the home of RU Premiership champions, Saracens (kick-off 6pm).
It will form part of a Festival of Rugby League which will also include a curtain-raiser between London Skolars and North Wales Crusaders (kick-off 3pm) and help spread the RL gospel in the capital city..
The festival marks one of three scheduled 'home games' for the Wolfpack taking place in the UK early in the 2020 season and will see the club bring a distinctly Canadian flavour to the capital.
The London Series will be action-packed both on and off the field with plenty of Canadian-themed entertainment on hand as well as delicious food and a family-friendly atmosphere.
Martin Vickers, Toronto Wolfpack UK general manager, said: “The London Series is a particularly special day on the Wolfpack calendar and already we are extremely excited to see it taking shape.
"We are delighted to be partnering with London Skolars to make the day possible and we also extend our gratitude to Saracens for the use of their home ground and their generous hospitality. ''
Martin added:"The chance to do battle with Super League powerhouse St Helens is also a mouth-watering prospect and we look forward to welcoming them and their fans to Allianz Park.”
As well as celebrating the first time the Wolfpack and St Helens have ever met on-field, the game will also mark Wolfpack recruit Sonny Bill Williams’ maiden contest in London as a Toronto player..
The world-renowned athlete has represented New Zealand in the UK capital on multiple occasions, including a 2013 Rugby League World Cup semi-final win over England the All Blacks 2015 Rugby Union World Cup victory over Australia at Twickenham.
The Wolfpack’s Super League round five fixture will also see second-rower Jon Wilkin come face-to-face with his former side for the first time.
After more than 400 games for Saints, who he joined from Hull KR at the end of the 2002 season, the 35-year-old Wilkin will run out against many old friends at the London Series in what is sure to be the beginning of an enduring rivalry between the two clubs.
Tickets for the 2020 London Series will be available in the coming weeks from Saints and www.saracens.com
Saints' Betfred Super League showdown at Warrington Wolves has been switched from Thursday, June 25, to Sunday, June 28 (kick-off 7.45pm).
The change has been made due to the previous week-end being designated to cater for international fixtures which could involve England.
Should the game be played anywhere other than the UK, it could mean that players from either club, who are selected for England, not being available due to travel commitments and insufficient recovery time.
Both clubs and Super League have taken the proactive step to move the fixture now rather than face a situation where neither team was able to field its strongest squad, or move it to the 11th-hour based based on international team selection. It will, however, still be screened by Sky.
GOLDEN point extra-time will be available in all Betfred Championship and League 1fixtures in the forthcoming season, but with a different twist.
When the games are level at the sounding of the final hooter, each team will take one point for earning a draw with a third competition point available to the first team to score in two five-minute periods of extra-time.