London Irish maintained their 100% record in Pool One of the Heineken Cup with a victory over Perpignan as the French side paid the price for their indiscipline.

Perpignan conceded two tries after having players sin-binned as London Irish kept up their winning ways in the competition.

The yellow cards led to a first defeat in the clash between the group's two form teams.

But the spectators were not treated to the attacking rugby which had seen Irish take a maximum 10 points from their opening two matches as Perpignan collected nine.

The opening Irish try came in the 21st minute when their pack drove lock Bob Casey over following a line-out after Perpignan's early replacement back row forward Gerrie Britz was the first of four players sent to the sin-bin following an offence at a ruck.

The French side were further depleted at the time with flanker Viliami Vaki receiving treatment in the other half of the pitch.

In the second half the home side restored their lead with the visitors again depleted after lock Rimas Alvarez Kairelis was yellow-carded for offside.

He was quickly followed by substitute prop Nicolas Mas for his part in illegally pulling down the Irish drive as the home side were awarded a 60th-minute penalty try which full-back Peter Hewat, who had already kicked two penalties, converted for an 18-16 lead.

In between an unconventional, but highly effective piece of skill from Perpignan's left-wing Adrien Plante had temporarily turned the game his team's way.

Seven minutes into the second half replacement half-back Cedric Rosalen floated a big crossfield kick in the direction of the unmarked Plante who deftly volleyed the ball over the line before diving on it for his side's only try.

Full-back Jerome Porical, who had landed three penalties in the first half, converted and Perpignan, leading 16-8, looked set to hand Irish their first European defeat of the campaign until their poor discipline came back to haunt them.

Things went from bad to worse for the French team with Hewat kicking two more late penalties to take his personal contribution to 14 points.

The second, which was the last kick of the game deep into injury time, deprived Perpignan of even the consolation of a losing bonus point.

One Irish player also spent 10 minutes in the sin-bin as Scottish referee Malcolm Changleng, who brandished four yellow cards altogether, punished David Paice for needlessly pushed Alvarez Kairelis following one of far too many infringements.

The Exlies' victory was far from pretty but it puts them firmly in control of their qualifying group.