London Irish's impressive unbeaten run in this season's Heineken Cup came to a painful halt in the snow at Perpignan's Stade Aime Giral as they lost 23-6.

The Exiles cling to a one-point lead over their French rivals in Pool One despite the defeat but they will be looking for 10 points from their remaining games against Treviso and Newport Treviso to secure a quarter-final berth.

Any fewer and Perpignan would be odds-on to finish in front in late January.

World Cup-winning full-back Percy Montgomery made an earlier than expected debut for the Catalans side, but his troublesome knee injury meant fly-half Cedric Rosalen took over the goal-kicking duties, and he kept his head to slot 11 crucial points.

Rosalen scored the only points of the opening quarter, slotting a penalty goal after London Irish lock Nick Kennedy was ruled off-side at a ruck.

London Irish full-back Peter Hewat levelled the scores on the half hour after a Perpignan ruck infringement, before Perpignan's England prop Perry Freshwater flicked an elbow at Kieran Roche, forcing the Exiles flanker off the field with a suspected fractured cheekbone.

The two sides emerged from the half-time break locked at 3-3, and Rosalen's second shot at goal gave the Catalans side a hard-earned and probably deserved lead.

Their cause was helped immeasurably in the 47th minute when Exiles centre Delon Armitage produced a reckless high tackle on Adrien Plante.

The Perpignan winger went down heavily and Armitage began trudging to the sideline before referee Carlo Damasco produced the inevitable yellow card.

London Irish shrugged off the one-man disadvantage as Hewat levelled the scores with his second goal.

But Perpignan's superior numbers told as Christoph Manas collected a slip pass from Rosalen to score under the posts.

Rosalen shrugged off two consecutive misses at goal to convert from in front, as the game began to take its toll on its international players.

London Irish skipper Mike Catt went off at half-time, Freshwater lasted barely 10 minutes of the second spell, Montgomery was gone after an hour and Scottish star Chris Cusiter was replaced moments later.

Rosalen took his side two scores clear with a penalty goal in the 72nd minute.

Perpignan's power began to reap dividends as a superbly worked rolling maul powered over the Exiles' try line.

Scotland international Nathan Hines emerged from the heap of bodies with the ball for a try which secured a home victory.