It was harsh on Gloucester who had looked the more likely to emerge triumphant with the likes of Mills, May and Trinder all showing up well on the night but credit to the visitors for never giving up.
Conditions were far from perfect with heavy rain falling from the off and an error strewn opening 10 minutes saw only a well struck penalty from Ryan Mills trouble the scoreboard.
That said, it had been a pretty passionate start to the game with some huge hits coming in from both sides although Dan Williams caught the eye with some powerful runs.
A rare piece of silky running almost opened up the visitors as the first quarter drew to a close with Henry Trinder making the break and good ground but Mills pushed the resulting penalty across the posts.
The visitors tried to step it up a gear and the much travelled Epi Taione trying to muscle his way through the defensive line on occasion but the Gloucester tacklers were up to the task at this point.
Gloucester came closest to a score as half time approached when Jack Hayes ran through onto Ryan Mills grubber kick which was fumbled by the Irish full back but the young centre lost the greasy ball when he seemed set to score.
And the well conditions denied Gloucester again just moments later when Jonny May returned a kick downfield and freed Kyle Palm who tried to draw the last man and put Hayes in for the score but the ball squirted loose as the pass was made.
Somewhat against the run of play, Irish levelled with the last kick of the game as they broke downfield and Jamie Lennard slotted a tricky penalty from in front of the Shed.
Incredibly, after a half with no tries, the second started with one after 20 seconds as Jonny May charged down a box kick, hacked on and won the chase to score. Mills' conversion hit the post and stayed out but Gloucester had an 8-3 lead.
Gloucester's backs were starting to look more threatening and Mills put Voyce away after a nice loop with Henry Trinder but the full back couldn't quite beat the last man.
Mills was off target with a couple of long range penalties as Gloucester tried to extend their lead and May and Trinder showed their class with dangerous breaks but a further score remained elusive.
With just 4 minutes remaining, Mills made it 11-3 with a simple penalty after Trinder nearly wriggled through but Taione crashed over in the corner to make it interesting and second row Kieran Low spun off a rolling maul to dive over and snatch the game for the Exiles five minutes into injury time.