Matt Peet will lead out his home-town team in the Betfred Challenge Cup final in his first season as head coach after Wigan hauled themselves off the ropes to claim a stunning 20-18 victory over holders St Helens.

The Warriors dominated the first half of their semi-final at Elland Road to lead 14-0 but looked to be on their way out when holders Saints, completely out of sorts in the first 40 minutes, found a purple patch and ran in three converted tries to go in front.

But winger Liam Marshall settled a pulsating tie with a spectacular 90-metre try – his second of the match – to secure a trip to the Tottenham Hotspur Stadium on May 28.

Peet, at 38 the youngest head coach in Super League, began the season largely as an unknown after being promoted from within to succeed Adrian Lam but he is now guaranteed a place in the club’s glorious history as they prepare to make a record-extending 33rd Challenge Cup final appearance.

Saints were desperate to retain the trophy and coach Kristian Woolf decided Jonny Lomax had recovered sufficiently from a bicep injury sustained in the last match to take his place in his starting line-up but he looked anything but as he slotted into the full-back role on defence with his arm heavily bandaged.

Lomax tried to pull the strings on attack but Saints were disjointed for most of the first half half despite the willing efforts of utility back Jack Welsby and 22-year-old Ben Davies, who was making only his fifth senior appearance in the absence of Lewis Dodd, Will Hopoate and Regan Grace.

Winger Josh Simm’s failure to catch Cade Cust’s high kick gave Wigan a dream attacking position and they made the most of it as centre Jake Bibby created the chance for Marshall to cross for the opening try with just two minutes on the clock.

Fumbles by Liam Byrne and Harry Smith enabled Saints to set up camp inside the Wigan half and they were pressing for an equalising score when the game took its first dramatic turn.

Right winger Bevan French looked a certain scorer after pouncing on a loose ball 20 metres from his own line but Welsby got back to halt his progress with two ankle taps as he was eventually brought down just short of the Saints line.

However, St Helens second rower Joe Batchelor was sent to the sin bin for holding down French in the tackle and Wigan took advantage of the extra man as Cust dummied his way over for their second try.

Smith was wide with both conversion attempts but the Warriors extended their lead after 28 minutes when second rower Liam Farrell – the England forward who is in the form of his life – wrong-footed the St Helens defence to sprint through a yawning gap for a third try.

Smith made it third time lucky with the conversion attempt as Peet’s men led 14-0 at the break.

As well as being clinical on attack, Wigan were energetic and accurate in defence and Saints’ only threat came just before half-time when centre Mark Percival collected Lomax’s kick over the defence on the last tackle but was tackled short of the line.

Whatever Woolf said at half-time did the trick, though, as they blew the game wide open with two tries in three minutes.

Burly Tongan centre Konrad Hurrell proved unstoppable after taking Welsby’s pass 10 metres out from the line to score the first, while winger Tom Makinson palmed the ball back into the grateful arms of Lomax, who had hoisted the high kick, for the second.

Makinson kicked both conversions to bring his side to within two points and Saints went in front after 56 minutes when skipper James Roby scored an opportunist try, belying his age with a mazy run that took him all the way to the line.

Makinson’s third goal took him to 999 points for St Helens and made it 18-14.

But the game took another final twist after 68 minutes when Marshall swooped on a loose ball after Lomax’s pass failed to find Welsby and went on a 90-metre sprint for his second try that put Wigan back in front and on their way to the capital.