Gloucester had shown moments of real class. However, having scored two decent tries through Jonny May and Charlie Sharples, they allowed Mont-de-Marsan back into the game through a combination of indiscipline and errors.
The visitors grew visibly more confident by the minute, as they perhaps sensed that a shock win was on the cards. They changed the point of contact skillfully with some slick offloading and kept the Gloucester defence on their toes.
And in Jean Baptiste Claverie, they had a fly half who had certainly packed his kicking boots. Claverie booted three penalties and a conversion to keep his team in touch.
It was a different matter in the second half though, as Gloucester took an iron grip on the game and the visitors barely made it into the Gloucester half in the second 40 minutes.
The pressure grew and, eventually, Mont-de-Marsan cracked. Two yellow cards hurt them badly and Gloucester ran in three second half tries to clinch a home quarter final.
The final scoreline perhaps flattered the Cherry and Whites a touch. But, a win's a win and Gloucester can now sit back and wait to see who they will meet in the knock out stages.
With players like May and Trinder feeling their way back after injury, both scored two tries today, there is plenty to be positive about.
A phenomenal effort by the Gloucester staff saw this game get underway, despite Friday's heavy snow, without issue at Kingsholm, although it was a bitingly cold afternoon.
A powerful start from the home pack, saw Gloucester get off to a promising start with a Freddie Burns penalty. But this was immediately cancelled out by Claverie as the referee saw obstruction at the restart.
An entertaining passage of play followed as Gloucester sought a breakthrough. Robson, Hamilton and Burns all made good ground, but the final pass was lacking.
An easily kickable penalty at goal was turned down, and Gloucester made it count. Slick hands on the left from Savage gave Jonny May a few inches of space, and that was all he needed to touch down in the corner for an 8-3 lead.
Gloucester were then dealt a blow as Freddie Burns, who was tackled heavily in the build up to the try, limped off to be replaced by Billy Twelvetrees.
While Gloucester were still reorganising, Claverie slotted his second penalty and then almost caught cold after a great break from deep from full back Durquet, the visitors held up over the line as they sensed a shock try.
The Gloucester pack produced a superb shove to disrupt the scrum, but a penalty was conceded at the ensuing ruck, and Claverie's third penalty gave his side a 9-8 lead after 19 minutes.
Nigel Davies' side responded with a good phase of play, backs and forwards both carrying the ball well, and Twelvetrees restored the lead with a 22nd minute penalty.
Twelvetrees then struck with ball in hand, as he sliced open the visitors defence with a superb break from halfway. Charlie Sharples was on his shoulder and the flying winger had too much pace for the cover and sprinted over in the corner.
It opened up a little daylight at 16-9, but Martyn Thomas' clearance was superbly returned by Fiji Sevens star William Ryder. He evaded tackles, made good ground and flanker Brethous crossed in the corner. Claverie's superb conversion levelled the scores.
There was an air of frustration around Kingsholm, but the visitors were playing well, arguably better than Gloucester, and Nigel Davies' side simply couldn't afford to play as loosely as they were at this point.
Claverie was off target with a drop goal as half time approached, but Gloucester then produced a great spell of play, which deserved better than Thomas being tackled into touch near the corner.
Half time came with no further addition to the score, and Gloucester went into the dressing room to regroup.
The visitors had proved themselves to be a dogged opponent and deserved to be on level terms at the interval. If they had been underestimated coming into the game, they certainly weren't now.
Once again though, there was the nagging feeling that the Cherry and Whites were contributing to their own problems with an error count that was far too high, and this had to be resolved quickly.
Gloucester could point to some curious refereeing decisions, and the loss of their playmaker, but a good second half performance was needed.
The early signs weren't promising as the handling errors continued, a key one coughing up possession in the Mont-de-Marsan 22 after a quickly taken tap from Dan Robson had the visitors on the ropes.
Ironically, an error then very nearly led to a try. An overthrown lineout confused the French defence, but Sharples was denied a second try by a forward pass.
The pressure did eventually get a result though, as Twelvetrees slotted a 51st minute penalty for a ruck offence for which replacement prop Phelipponneau was yellow carded.
Gloucester now had a spring in their step, and a lightning break from Sharples set up great field position, just five metres from the Mont-de-Marsan line after Kalamafoni was held up over the line.
The pack tried to bludgeon their way their way over, but it was the rapier of Henry Trinder who finally sliced his way to the line to open up a 24-16 lead.
And it was Trinder who clinched the bonus point on 64 minutes, as Thomas made a break down the right and found the supporting centre with his inside pass.
Cabannes was next to see yellow for pulling a man back off the ball, and the freezing Kingsholm crowd were delighted to see their team starting to move the ball around with pace and confidence.
Jonny May finished things off as he latched on to a superb break from Huia Edmonds and sprinted clear.
There's still so much yet to come from Gloucester, that's obvious. However, there's still an awful lot of rugby left to play and a lot to play for.
|Gloucester Rugby Score Card|
|Mont de Marsan Score Card|