Josh Griffin sent off for Hull FC
Saints last lifted cup in 2021 and have won past four Super League titles
FT: Hull KR 28-10 Salford - Robins first team into semis
Wigan v Warrington & York v Leigh in other quarter-finals on Sunday
FT: Hull FC 18-32 St Helens
Image source, PA MediaSo a frantic Challenge Cup tie comes to an end.
St Helens join Hull KR in the hat for the semi-finals.
Wigan face Warrington and Championship side York City Knights face the Leigh Leopards in tomorrow's two other quarter-final ties.
We'll be back tomorrow afternoon when the action returns.
For now, thank you for joining us.
Wigan v Warrington (Sun, 14:30 BST)
Two down, two to go.
The Challenge Cup quarter-final action continues on Sunday, when Wigan take on Warrington live on BBC One.
You can read a preview of that game by clicking here.
Wigan Warriors boss Matt Peet says their Challenge Cup quarter-final against Warrington Wolves is a chance to return to their best.
Read MoreFT: Hull FC 18-32 St Helens
Hull head coach Tony Smith, speaking to BBC One:
"I'd rather talk about the effort everybody put in, discipline cost us not only in that [the red card] but other instances.
"Saints were too good but I’m proud of the effort put in by all the players.
"It is what it is, there’s no use dwelling on things, you get on with it, make adjustments and try to do something special.
"Saints were that little bit too good, they’re clinical and they know when there is blood in the water, but I’m proud of my guys."
FT: Hull FC 18-32 St Helens
Image source, PA MediaSt Helens' player of the match Jack Welsby, speaking to BBC One:
"We picked up a couple of key injuries early on but this team’s got resilience and we showed that today.
"They threw the ball about well and they’re a tough team and thankfully we came out on the right side of it today.
"We didn’t talk about the sending-off as we knew sometimes that galvanises a team so we concentrated on ourselves.
"We’re on the right track, there are some things to improve and hopefully we can achieve that when we play the semi-final."
FT: Hull FC 18-32 St Helens
Callum Thompson: Davy Litten has been a shining light for Hull FC on a tough afternoon. Consistent with that ball return out the back every single time.
Ben Sherlock: Jack Welsby could literally miss 100 tackles, knock on every time he touches the ball and Saints concede 500 points and still get man of the match.
No-one can deny that Jack Welsby had a positive impact on his tie for St Helens...
FT: Hull FC 18-32 St Helens
Image source, PA MediaA great game for a neutral.
The Challenge Cup never disappoints.
Hull FC 18-32 St Helens
John Kear
Wales coach on BBC One
They have been absolutely ruthless and relentless, and come away with a great victory.
Hull FC 18-32 St Helens
Image source, SWPix.comA cracker of a Challenge Cup tie comes to an end.
It really was a tie that had it all. From a frantic first half ending all square, to Josh Griffin's quickfire yellow and red card, to a brief Hull comeback followed by a clinical St Helens performance sending them through to the semi-finals.
Hull's race is run. The Saints go marching on.
Hull FC 18-32 St Helens
Alan Hunte
Ex-Great Britain winger on BBC Radio Humberside
Pressure and time telling, that’s what it is.
Hull knowing they have to push the envelope and turning the ball over cheaply and not making St Helens waste energy, while wasting too much of their own in defence.
James Bell
Image source, PA MediaSt Helens storm through to wrap up the win and their place in the Challenge Cup semi-final.
Lewis Dodd offloads to Jonny Lomax who works it to James Bell, who runs in at the corner.
Clinical.
What's not clinical is Joey Lussick's kicking. He sends it wide again.
Hull FC 18-28 St Helens
Curtis Sironen works the ball back into the Hull goal area but he's well held up before he can get the ball down for his second St Helens try.
The hosts aren't sitting back despite the scoreline and Saints' player advantage.
Hull FC 12-28 St Helens
John Kear
Wales coach on BBC One
Even for this Hull side, it’s one step too far now.
St Helens’ professionalism has been first class.
Hull FC 18-28 St Helens
Hull's kick-off fails to go past the 40 and St Helens win possession back.
Not a great restart from the hosts.
Hull FC 12-28 St Helens
Matt Newsum
BBC rugby league commentator on BBC One
That is a crushing blow for Hull and a big step towards the semi-finals for Saints.
Jack Welsby stands tall.
He’s delivering in big moments.
Jack Welsby
Image source, PA MediaAn absolutely stunning clutch play from Jack Welsby. St Helens show their class once again.
Soon after the restart from Jake Trueman's try for Hull, Saints go straight on the attack.
They get to within inches of the line within just one tackle and eventually Welsby crashes over. That's why he's possibly the most highly rated man in Super League right now.
Joey Lussick misses the extras, however.
Hull FC 18-24 St Helens
Richard Stead
BBC Radio Humberside commentator
Absolute carnage in back play!
Tee Ritson and Jack Welsby going for the same ball.
The ball comes loose and Jake Trueman benefits.
Can they? Will they? Well, they might!
Jake Trueman, goal Liam Sutcliffe
Image source, PA MediaThey couldn't, could they?
St Helens' Tee Ritson spills a high ball as he goes to claim it at the same time as Jack Welsby - who unhelpfully comes racing in - and Hull pounce, first through Carlos Tuimavave.
Then again through Jake Trueman who goes over in the in corner.
Liam Sutcliffe adds the two and 12-man Hull are back in this game.
Hull FC 12-24 St Helens
Jodie Cunningham
St Helens and England full-back on BBC One
Image source, SWPix.comYou can't fault the effort from Hull but that was quality there from Tee Ritson.
Hull FC 12-24 St Helens
Alan Hunte
Ex-Great Britain winger on BBC Radio Humberside
Image source, SWPix.comThe scrum-half Lewis Dodd reaping the rewards of the winger Tee Ritson.
It was a bomb that went up and there was no real chase, Ritson was always going to get to it and he showed good pace before being pulled down.
Saints put in two passes to Dodd who steams on to ball against a fractured defence and put the ball down.
Hull FC 12-24 St Helens
Hull look tired now.
St Helens could really do some damage with 20 minutes to spare.