Gloucester began with only two of the team which started last Saturday on the pitch and made the worst possible start when Vannes’ Romaric Camou broke clear and found fellow winger Benmegal, who dived over flamboyantly inside the first 50 seconds.
The Cherry and Whites barely had time to compose themselves before hooker Theo Beziat managed to bundle through some weak challenges to head towards the line once more.
The Frenchman was able to offload to Kiwi scrum-half Ruru, who dived over one-handed to put the hosts 14 clear with less than four minutes on the clock.
The visitors responded instantly, however, and George Barton found a gap, allowing skipper-for-the-night Harris to reduced the arrears.
But four minutes later Ruru restored the hosts’ two-score advantage when he pounced on a loose ball to dive over from a yard following a good line-out.
It took well until the first half for Gloucester to impose themselves and when Barton tried to weave through a tight gap, Beziat was sent to the bin for 10 minutes for foul play.
They were unable to make the man advantage pay, however, as a scrappy end to the half saw Vannes go in to the interval 12 points ahead.
Wonderful play from from right to left seven minutes into the second half, allowed Benmegal to score his second in the corner and effectively put Vannes out of sight.
To their credit, Gloucester’s heads did not drop and following a meandering run from Reeves, scrum-half Charlie Chapman handed to substitute Blackmore beside him to find the gap and dive over under the posts.
Vannes momentarily lost their composure and after a fantastic dummy from Will Butler, the centre’s pass allowed Jake Morris to score the simplest of tries in the right-hand corner and make it a seven-point game.
The French club responded with Chateau powering over from a driving maul and Gloucester’s Freddie Clarke was then sin-binned for the rest of the game for coming in from the side.
A carbon copy of their fifth try mere seconds later allowed Blanchard to add a sixth for Vannes, who put poor current domestic form to one side to inflict a bruising defeat on their less experienced opponents.
