The formality that was supposed to be Celtic’s victory at the Falkirk Stadium never came close to unfolding yesterday. In a match that bore not the slightest resemblance to any Eddie May’s side have been involved in this season, three goals were scored by the home side, six in total, and every one of them in a ridiculously entertaining second half that throbbed from start to finish. Nobody saw this one coming.

Falkirk’s previous four points had all been courtesy of scoreless draws. The Clydesdale Bank Premier League’s bottom club had scored only twice in their last eight games. But here they were, responding to the loss of an early second-half goal by turning the game on its head, and when the visitors responded in kind — with two goals by the substitute, Scott McDonald — they somehow found it within themselves to unearth a late equaliser.

With five minutes left, their substitute, Mark Stewart, latched on to Ryan Flynn’s ball over the top and thundered it past Lukasz Zaluska with his left foot. It was a fitting finish to an afternoon on which Falkirk had utterly dominated the first half, despite a catalogue of injury problems that included one in the warm-up to their only striker, Carl Finnigan. Pedro Moutinho, the midfield player, who had yet to play in his second spell with the club, was asked to deputise, and scored Falkirk’s second goal.

None of which says much for Celtic. With Marc-Antoine Fortuné making his first start after long-term injury, they missed a penalty just before half-time, were all over the place at the back, and twice squandered a second-half lead. Tony Mowbray’s side, now just two points clear of Rangers, who have a game in hand, were are as slow out of the the blocks as the few hundred supporters who remained outside the stadium until after the minute’s silence for Remembrance Sunday.

Celtic struggled all day to handle their opponents’ numerical superiority in midfield. Young Alex MacDonald, who has shed a few pounds since arriving on loan from Burnley, seems to be growing in confidence by the week, and revelled in the freedom he was given here. Ryan Flynn was another in his element.

Falkirk, in fact, were all over their opponents in a first half that made a mockery of the teams’ league positions. Brisk and brave, they pinned their opponents back, and lacked only the quality up front that would have created better chances.

Apart from a deflected shot by Aiden McGeady, Celtic created nothing until the stroke of half-time, and even that was their opponents’ doing.

MacDonald, of all people, brought down Danny Fox in the penalty area, and the referee, Brian Winter, pointed to the spot. While the award was fair, a goal would have been more than Celtic deserved, which is why Robert Olejnik’s remarkable double save appealed to the neutral. Not only did he block McGeady’s spot-kick with a low dive to his right, he was alert enough to deal with the rebound. Just when McGeady seemed to have bundled the loose ball beyond him, the goalkeeper thrust out a leg and somehow spiralled it over the top. His team-mates congratulated him with such enthusiasm that they almost forgot to defend the subsequent corner.

Celtic couldn’t be as bad in the second half as they were in the first, and sure enough, with Stephen McManus on for Glenn Loovens, and Georgios Samaras suddenly applying himself, they started after the interval with new vigour.

When the Greece striker was hauled down by Brian Allison, Barry Robson hurled the free kick deep into the box, where Gary Caldwell rose unmarked to head it back across goal and into the corner of the net.

Falkirk were supposed to be demoralised at this point, frustrated by their failure to capitalise on earlier pressure, but a stroke of luck, just after the hour, got them back in the game. In the same position that Fox had taken a tumble in the first half, Caldwell brought down Flynn, and another penalty was awarded. This time, the goalkeeper was beaten, but only just, as Scott Arfield’s low shot squeezed inside the left-hand post.

Three minutes later, Falkirk scored again. Flynn again surged into the box, this time unchallenged by his marker, before picking out Moutinho on the penalty spot. With his right instep, he diverted it past the flapping Zaluska.

Only 64 minutes had been played, but a few Celtic fans made for the exits, presumably lacking faith in their team’s ability to recover. That, though, was not to account for the arrival of McDonald, who came on for Robson, and single-handedly turned the match.

Within five minutes, he was on the end of a Fox cross, nodding it down into the ground and over the line. Nine minutes later, he was at it again, this time popping up at the back post, to sidefoot over the line from close range after a perfect square ball across the six-yard area by Samaras.

That they couldn’t see the game out from there will be a matter of some concern to their manager.