It was fourth time lucky for Glasgow after three “tries” had been disallowed by the television match official – this time a pass which looked suspiciously forward was not overturned.
Glasgow were boosted by the availability of their two prospective Lions, scrum half Ali Price and tighthead prop Zander Fagerson, though the latter may have questioned that decision when he endured a nervous time just ten minutes into the match.
He went into contact with his arm out in front of him to protect his head, unfortunately for him it went into the head of opposition scrum half Gonzalo Bertranou.
The move went on with full back Adam Hastings putting centre Nick Grigg over the line with a clever pass back inside, but the attention of the refereeing team then turned to the Fagerson charge.
After several looks it was decided it was just a penalty, anything more would have been harsh. Two quick penalties then saw the Dragons camped on the Glasgow line.
Two passes from a lineout gave impressive young centre Aneurin Owen a clear run to the line for the try, outside centre Sam Davies adding the conversion in what quite a turnaround in fortunes.
Davies also added another penalty and a drop goal – opposite number Ross Thompson replying with a penalty – to extend the Dragons lead before Glasgow scored their first try of the evening.
Having worked their way to the try line they tried to batter their way over while ignoring free players out wide. When they eventually spotted the space, right wing Kyle Steyn just had to catch the pass and job over.
In the build up Dragons captain Ross Moriarty had made a no arms tackle and he was sent to the sin bin.
On the stroke of half time Glasgow put together a truly superb team try which involved hooker George Turner twice, lock Scott Cummings and Price with some superb interpassing before Thompson took the final pass for the score.
That feeling got even better when left wing Cole Forbes went over, but the Dragons had spotted a knock-on and a captain’s challenge meant the score was chalked off.
Glasgow were not to be denied though and Turner, responsible for the knock on, made amends by finishing off a lineout drive, with Thompson converting from wide.
Glasgow thought they had a fourth when Price celebrated his Lions call-up by going over, but another TMO decision ruled it out for blocking – but McDonald then popped up to seal the bonus point victory.