If a team are to have a bogey ground, it is not useful for it to be the place where trophies are handed out. Neil Lennon has grown weary of discussing troubled afternoons for Celtic at Hampden Park. Ross County, Kilmarnock, Hearts, Rangers and now St Mirren have ended Celtic silverware aspirations at the national stadium since Lennon became the manager.

In this instance, Lennon was rightly scathing of a Celtic display that could be generously described as lethargic and, otherwise, classed as astonishingly bad.

In proving Scottish football may be many things but is not yet completely predictable, Celtic's supposedly straightforward run to a domestic treble was ended at the League Cup's semi-final stage. St Mirren fully merited their victory, which earns them a meeting with Hearts in the final on 17 March.

"That was a soulless performance from us," Lennon said. "We lacked intensity, desire and a will to win. Some of them behaved like spoilt kids out there. The treble has gone and we only have ourselves to blame. We will get criticism and rightly so; that was an impersonation of the team I know."

Lennon can be accused of many things, but never of sugar-coating dismal performances. "Defensively I thought we were awful," he said. "This seems to be a bogey ground for us but that is the worst we have played here. That was awful, from what I regard as top-class players. Maybe I have got it wrong, maybe I need to look at changing things before the [transfer] window closes."

As has proved common when Celtic struggle, indications of a poor attitude were apparent from the kick-off. Lassad and Georgios Samaras were sluggish in attack, Joe Ledley and Victor Wanyama lacked midfield drive and St Mirren triggered panic in the Celtic defence every time they attacked. Celtic's goalkeeper, Lukasz Zaluska, looked unconvincing.

In contrast, the zest displayed by St Mirren, epitomised by John McGinn, Esmaël Gonçalves, Steven Thompson, Gary Teale and Conor Newton, belied their status as the team second from bottom in the Scottish Premier League.

Gonçalves, making his debut, clipped home St Mirren's opener when meeting a Newton cross. Celtic offered hints at a reply via Scott Brown, Gary Hooper and Samaras but were never convincing.

It was a surprise that Celtic snatched an equaliser just seconds before the break. Hooper converted from close range after smartly evading the St Mirren defence, with Brown the supplier.

Within five minutes of the restart, Celtic were fortunate to be afforded a chance to go in front. Jim Goodwin was harshly adjudged to be guilty of handball from a Lassad shot; justice was done when Craig Samson batted away Charlie Mulgrew's tame effort from the spot.

There was less argument about the next penalty, Mulgrew this time clearly benefitting from the use of an arm. Paul McGowan, once of Celtic, coolly slotted past Zaluska.

To their credit, St Mirren did not settle for that advantage. Thompson claimed their third, with a volley from Marc McAusland's cross that Zaluska will feel he should have done better with.

Celtic never looked to carry sufficient threat to haul themselves back into the tie. They did score again, Mulgrew concluding his eventful game by shooting home from outside the penalty area but it was too little and way too late for Celtic. St Mirren had secured a first Hampden win since they claimed the Scottish Cup here in 1987.

"This is a monumental result for us," said Danny Lennon, the St Mirren manager. "The players were different class. We were inspired by previous St Mirren wins over Celtic, right back to 1959.

"The message we gave the players was to be fuelled by the belief that it can be done. We were probably written off by everyone in the media. That is something we have to deal with, as a small club playing the best team in the country. The gulf between Celtic and ourselves is enormous. But the same so-called experts wrote us off against Aberdeen in the quarter-final. They said it couldn't be done but here we are, in a final."

St Mirren are indeed within 90 minutes of glory; Celtic must divert their attention towards alternative prizes.

Man of the match John McGinn (St Mirren)