In qualifying as the top seeds for the last eight of the Heineken Cup, Northampton won six pool matches out of six, culminating with this three-try victory. Seven teams have achieved a clean sweep before and not one went on to the final, never mind winning the cup. Saints' attempt to break the duck will begin with a home quarter-final against Ulster in April. Yesterday's semi-final draw, giving Saints a tie in England with Perpignan or Toulon if they knock Ulster out, offered the 2000 champions a fantastic shot at making it all the way.
"Home" is a word in need of its own qualification. A Heineken Cup quarter-final venue must have a minimum 15,000 capacity, and Saints' Franklin's Gardens is short at 13,591. A switch to the 22,000-capacity Stadium MK in Milton Keynes, 20 minutes away, looks certain.
Some Saints supporters poured scorn over the ability of the uncapped midfielders Steve Myler, James Downey and Jon Clarke to mix it with the best later in the competition. It will be hotter stuff, in both the sporting and climatic senses, in April. The injured England duo Courtney Lawes and Chris Ashton should be back by then; Ashton, according to director of rugby Jim Mallinder, is ready to face Wales on Friday week after missing two matches with a quad injury.
This was Castres' first home defeat of the season, and Northampton led 15-0 after 25 minutes, with tries by Joe Ansbro and Phil Dowson, and a conversion and dropped goal by Myler, while Calum Clark, normally a flanker, gave a great impression of a hard-nut lock. Northampton's third try was a beauty. Mark Sorenson, Jon Clarke and Dowson counter-rucked over the Castres centre, Pierre-Manuel Garcia, and Ansbro, Clark and Dylan Hartley interpassed on the short side up the right wing. Ansbro was tap-tackled by Yoan Audrin but Ben Foden applied the finish. Myler's penalty made it 23-7 and Sébastien Tillous-Borde's try from a scrum came too late.
"Going away and playing quarter-final rugby is not easy," said Hartley, referring to last season's defeat by Munster in Limerick. "Closer to home we'll be able to pack it out and it will be a big occasion for us."
Scorers: Castres: Tries Bernard, Tillous-Borde; Conversion Bernard. Northampton: Tries Ansbro, Dowson, Foden; Conversion Myler; Penalty Myler; Drop goal Myler.
Castres: F Denos; M Nicolas, Y Audrin (R Martial, 61), P-M Garcia (S Bai, 72), V Inigo; P Bernard, S Tillous-Borde; M Coetzee (A Peikrishvili, 60), B Kayser (A Giorgadze, 52), D Saayman (L Ducalcon, 67), S Murray, R Capo Ortega, C Masoe (capt; G Adamou, 52), S Malonga (I Tekori, 80), J Bornman.
Northampton: B Foden; J Ansbro, J Clarke, J Downey (B Reihana, 67), P Diggin; S Myler (S Geraghty, 78), R Powell (S Commins, 78); S Tonga'uiha (A Waller, 72), D Hartley (capt; B Sharman, 69), B Mujati (T Mercey, 72), C Clark, M Sorenson (C Day, 57), P Dowson, T Wood (M Easter, 67), R Wilson.
Referee: P Fitzgibbon (Ireland).