Gregor Townsend put paid to Munster's unbeaten Heineken Cup record with an impressive performance at Stade Pierre-Antoin on Saturday.

The authority of the Scottish fly-half enabled his side to pull out a victory that sees Castres top Pool 4 and offers them a chance of a home draw in the quarters.

Munster were never on their best behaviour in a game that saw them waste the chance to top the group.

At least they have a place in the knock-out stages, albeit away from home with the possibility of facing Leinster in Dublin.

Munster found themselves 13 points in arrears after 20 minutes as the fired-up Frenchmen took their chances.

While Ronan O'Gara missed one opportunity to get his side going when he fluffed an easy penalty, Castres full-back Romain Teulet was on the mark in seventh minute.

The influential Teulet doubled that score in the 16th minute before Castres scored the first try of the game five minutes later.

Munster failed to spot their jumper, and from the line-out steal, Castres moved the ball right, then left, before Townsend put Teulet through the gap to score and convert.

Munster, unable to get their normal continuity game flowing, finally got on the scoreboard when O'Gara rifled over a penalty in the 25th minute.

The game was in danger of boiling over on the hour after Munster prop Peter Clohessy was bitten on the arm.

Castres flanker Romain Froment was yellow carded after throwing a punch at Anthony Foley as Munster started to put pressure on the Frenchmen.

Then on the stroke of normal full-time O'Gara dummied his way through to set-up replacement David Wallace with a try.

O'Gara converted to set-up a nervous final few minutes for Castres.

But in the fifth minute of injury-time Castres found space out right to give replacement Oliver Sarramea a try in the corner.

Castres: Tries: Teulet, Sarrema; Pens: Peulet (3); Cons: Peulet.

Munster: Tries: Wallace; Pens: O'Gara (2); Cons: O'Gara.

Castres: R Teulet; U Mola, N Berryman, E Artiguste, S Longstaff; G Townsend, A Albouy; M Reggiardo, R Vigneux, B Moyle, N Spanghero, C Fernandez-Lobbe, A Costes, I Lassissi, R Froment.
Replacements: S Chinarro for Costes (38), W Delmont for Berryman (68); O Sarramea for Teulet (78).

Munster: D Crotty; J Kelly, M Mullins, J Holland, A Horgan; R O'Gara, M Prendergast; M Horan, F Sheahan, P Clohessy, M Galwey, M O'Driscoll, J Williams, A Foley, A Quinlan. Replacements: J Hayes for Horan (50), P O'Connell for O'Driscoll (50), D Wallace for Quinlan (65), D Hegarty for Staunton (77), J Staunton for Crotty (74), R Henderson for Mullins (65).

Referee: Tony Spreadbury (England).