London Irish saw off Northampton 30-18 to reach the Premiership Rugby Cup final for the second season running.

James Basham drove over to extend the lead, but two James Grayson penalties brought Saints back within two points at 20-18 going into the final quarter.

Jennings kicked a third penalty before Eddie Poolman’s late try sealed it.

Having lost last year’s drawn final on fewer tries scored, Irish will be aiming to go one better in a home final on 19 March, against the winners of Sunday’s semi-final between Exeter and Sale (13:00 GMT).

Fresh from his crucial score in Saints’ derby win over Leicester Tigers last weekend, winger Sleightholme soon added to his try tally when he grabbed Grayson’s cross-kick to touch down.

Yet the visitors, who gave a debut to former Wasps hooker Tom Cruse, then fell behind to an opportunistic try as Cinti charged down Litchfield’s clearance kick and finished in the corner.

Having been outdone in the opening 15 minutes, the Exiles worked their way back into the game, with marauding back rower So’otalo Fa’aso’o causing havoc, and Jennings’ shot at goal made it 10-5.

It was Saints’ turn to edge ahead against the run of play when Litchfield’s good line opened up the Irish defence for the first time to run in under the posts from 10 metres.

The Exiles saw a second Cinti score ruled out for a forward pass, but with the hosts playing advantage, Jennings kicked the penalty for a narrow but deserved lead with the last play of the first half.

Irish quickly opened up a two-score lead after the restart when Basham slammed over from close-range.

Yet the seesaw pattern continued as Saints fly-half Grayson, featuring for the first time since October after a foot injury, struck back-to-back penalties to set up a tense final quarter.

The Exiles’ dominance in the scrum eventually began to tell, and after Poolman won the turnover penalty which allowed Jennings to make it 23-18 with nine minutes left, the Australian centre then slid over for the killer score, fed by Matt Cornish.

London Irish assistant coach Declan Danaher told BBC Radio London:

“We spoke about bringing a focus to what we were doing in terms of the way we wanted to attack and then real intent in defence, and I think we did that.

“They kept pinning pressure back on us and I thought the bench coming on made a big difference.

“We’ve been calm all week, and, like I said, we asked for focus and intent, and on the back of that we knew we could get a performance that would take us to the final.

“It’s brilliant – I can’t wait. It’s St Patrick’s Day weekend, it’s going to be a great atmosphere and it’ll be a great way to finish off the weekend.”

Northampton Saints coach Matt Ferguson told BBC Radio Northampton:

“I thought they were strong all over really. We couldn’t get a foothold in the game and ultimately the best team won.

“They had complete dominance in the scrum and that falls with me, and we’ve got to do some work in that area and review what happened tonight.

“We genuinely came here to compete and put on a performance because that’s what we always do in a Saints shirt, and I just feel we couldn’t quite execute what we wanted to do, and right now that’s what hurts.

“The boys kept at it and tried to match their physicality, but ultimately the lesson is there that if your set-piece doesn’t function you don’t get a foothold, if you don’t get a foothold you’re under pressure.”

London Irish: Loader; Cinti, Williams, Jennings, Dykes; Atkins, Englefield Gigena, Ruiz, Chawatama, Caulfield, Munga, Cooke (c), Basham, Fa’aso’o.

Replacements: Cornish, Haffar, Parker, Scragg, Donnell, O’Sullivan, Poolman, Stokes.

Northampton Saints: Collins; Sleightholme, Hutchinson, Litchfield, Skosan; Grayson, Braley (c); Waller, Cruse, Petch, Nansen, Coles, Wilkins, Hinkley, Graham.

Replacements: Burns, Hobbs-Awoyemi, Painter, Lockett, Sylvester, James, Matavesi, Hendy.