Ulster had appeared to be on course to complete the treble over Hugh Campbell’s men – until a dramatic home revival just before the break.

Warriors snatched two converted tries, then produced a heroic defensive performance to seal the win.

Celtic Cup winners Ulster had given instant notice of their intentions by breaching the home defence with ease after just two minutes.

But Paul Steinmetz’s touchdown was snuffed out by referee Nigel Owens for a marginally forward pass from Adam Larkin.

The visitors kept up the early pressure and broke the deadlock with a Larkin penalty for a tackle offence inside the Glasgow 22-zone.

However the Warriors responded in positive fashion to level the contest with a long-range strike by Calvin Howarth, back in action after a shoulder injury.

The province looked the more controlled outfit as they strung together phases galore.

But with the Glasgow defence more assured, they had to rely on another penalty by Larkin to edge back in front.

The home troops also had to contend with the temporary loss of three players in quick succession, skipper Jon Petrie, centre Graeme Morrison and scrum-half Graeme Beveridge.

Ulster took full advantage by creating the first try, flanker Neil Best being driven over by his pack-mates in the wake of a penalty line-out.

Glasgow mounted a series of promising attacks of their own, featuring darts at the line by Glenn Metcalfe and Scott Lawson, but all they could show for their initial efforts was another Howarth penalty.

The home fans were cheering even louder on the stroke of the interval when wing Sean Lamont oustripped the Ulster defence from fully 60 metres for a wonderful solo score.

Even better was to come a minute later as Alan Bulloch galloped over following great work by Metcalfe and Rory Kerr. Howarth added both goals to complete the quickfire turnaround of fortunes.

Ulster’s plight grew deeper as skipper Andy Ward was yellow carded for preventing a quick penalty.

And within a minute Glasgow had grabbed their third try through Lawson in the wake of an expertly executed kick, chase and tackle by Metcalfe. Howarth again slotted the kick.

Matt McCullough went over for Ulster with Paddy Wallace converting to set up a tense finale.

And the jitters set in when Scott Young added another in stoppage time – but Glasgow held on.