Northampton Saints completed the double over Pool 1 rivals Cardiff Blues and maintained their 100 per cent record in the competition thanks to a 72nd minute try from replacement Calum Clark.

The home side were leading 16-12 when Kiwi Number 8 Xavier Rush was red carded for a dangerous tackle mid way through the second period and the English premiership side capitalised to take the victory in Cardiff.

Northampton fly-half Stephen Myler traded three penalties with Dan Parks in an error-shrewn opening half as both sides battled against the adverse weather.

Myler opened the scoring in the third minute after Northampton smashed their opponents at the first scrum.

Cardiff hit back through the reliable Parks on 14 minutes before Myler restored the Saints’ advantage at the end of the opening quarter.

The home side were boosted when Saints centre James Downey was yellow carded on the half hour mark for a blatant trip on Blues scrum-half Richie Rees.

Parks added his second penalty from close range before putting the Blues into the lead for the first time on 36 minutes with his third successful kick.

But Myler drew Northampton level on the stroke of half time with a routine penalty as the teams left for the dressing rooms at 9-9. .

British Lions and Wales star centre Jamie Roberts was introduced for his first appearance of the season at the break for Tom Shanklin.

Roberts made an instant impact in the build-up to the opening try of the match.

Centre partner Casey Laulala made the initial break and after Xavier Rush and Roberts forged their way towards the line, Rees and Parks combined to feed Richard Mustoe who shrugged off the challenges of Lawes, Dylan Hartley and Phil Dowson to touch down.

Parks converted for a 16-9 lead before the Blues pressed the self-destruct button.

Firstly, Bradley Davies was sin-binned in the 49th minute for illegally kicking the ball away from replacement scrum-half Lee Dickson.

Myler reduced the deficit with his fourth penalty before the turning point of the match. Northampton were attacking in the Blues 22 when Rush was dismissed for a dangerous tackle on Lawes.

Myler booted his fifth penalty to trim the lead to 16-15 but the 13-man Blues were on the ropes.

Davies returned from the cooler but Myler nudged the Saints ahead on 61 minutes with his sixth penalty.

But, three minutes later, Parks hauled the home side in front once again with a neat drop goal from in front of the posts.

The Blues displayed a strong defence but they were finally breached with eight minutes remaining when Clark burrowed over.

Myler missed the conversion and Clark almost went from hero to zero as he was sin-binned but Northampton clung on.