The Cherry and Whites flew out of the blocks, their rampaging pack bulldozing French hooker Olivier Azam over the Northampton tryline before the Saints had even got their hands on the ball, a huge 20-metre rolling maul from a line-out tearing a hole through the Saints' defence, as prop Rodrigo Roncero assisted Azam's flop over the line, Mercier adding the conversion from out wide on the left.
Northampton missed the influential presence of ex-All Black back row Andrew Blowers and England scrum-half Matt Dawson, but gave game resistence after their rocky start, New Zealand wing Bruce Reihana among those to impress throughout down the left flank.
Gloucester too were nearly without one of their talismans early on, after skipper Phil Vickery was seemingly knocked out by Saints' dynamic loosehead Tom Smith in an accidental head-to-head collision in a tackle. Vickery went off for a blood-bin, but apparently decided against the medical advice of the Gloucester staff and rejoined the fray soon after – a decision all the more controversial given that forwards coach Dean Ryan's epilepsy condition may have been caused by playing through concussions.
Vickery did however exert his influence in the set-piece throughout, his side going 10 points clear with a Mercier penalty from 30 metres as Northampton finally got their hands on the ball in midfield while struggling early on in the lineout.
Coach Wayne Smith's side made the breakthrough however on 19 minutes when former Scotland centre John Leslie straightened the line at pace from short range, getting on the end of a timely scissor from Grayson under the posts to dive over after breaking the attempted tackle of Mercier.
Grayson converted, but a second Mercier penalty after a previous miss saw the visitors go into the interval as 13-7 leaders, despite the likes of Budge Pountney applying pressure on the Gloucester half backs in their own half.
Grayson missed a long penalty as the second half got underway, and it was a snap drop-goal from Mercier that sent this game the way of the Cherry and Whites on 50 minutes, his low miscued strike putting them 16-7 to the good.
To their credit, Saints never laid down, and a Grayson penalty from infront of the posts got them back within shouting distance, although the sin-binning of No.8 Mark Soden for a high tackle did not help their cause as the Gloucester pack started to dominate – South African Jake Boer being a menacing presence throughout.
A further Grayson penalty with 15 minutes to go gave the sellout Franklin's Gardens crowd at least a glimour of victory, but despite Reihana's enterrise down the left-hand side in tandem with outside centre Peter Jorgensen, it was not to be their day as a bonus point was their only reward, against a Gloucester side now looking like champions elect.
Northampton SaintsTry: LeslieCon: GaysonPens: Grayson 2
GloucesterTry: AzamCon: MercierPens: Mercier 2DG: Mercier
By Mark Smith