A last-minute line-up change had seen Stephen Ferris withdrawn due to injury, replaced at Number Eight - a problematic position with Nick Williams, Robbie Diack and Roger Wilson already unavailable - by Mike McComish. Irony would have it that former Ravenhill favourite Pedrie Wannenburg ran out for the visitors in that very position.

Elsewhere, 20-year-old hot prospect Iain Henderson started in the back row, while Pienaar, Ulster's Heineken Cup top scorer last season with 80 points, was an exceedingly welcome addition to the replacements bench, back at Ravenhill after two months away on Four Nations duty for South Africa.

After Castres full-back Romain Teulet had opened the scoring on five minutes with an acutely-angled penalty from the left wing, Paddy Jackson had only 90 seconds to wait before he was able to slot home a kick of his own from the Castrais' '22'. Then, when Jared Payne latched onto a loose ball on half-way seconds after the Frenchmen's restart, the full-back illustrated that his rich vein of Pro12 form had effortlessly made the transition to the Heineken Cup, as he left three men for dead in the blink of an eye. Payne advanced to just inside the '22', supplied Trimble on the left wing with precision, and the Ireland man went over in the corner. Jackson's conversion made it Ulster 10 Castres 3 on 10 minutes.

An errant penalty from the 10-metre line by out-half Pierre Bernard came and went, before Jackson got his angles just right with his second penalty, earned at the culmination of a sublime Ulster passing move which deserved more than a meagre three points. A scintillating burst through the middle from Tommy Bowe on 19 minutes then got Ravenhill back on its feet, but the quicksilver winger ran out of room as he was forced into touch just shy of the corner by diligent Castres defending.

It proved only a brief respite for the visitors however, as three minutes later the ever-alert Marshall dashed under the posts to ground the score after his own inspired chip forward, which seemed to have taken everyone in a blue jersey by complete surprise. Jackson dispatched the extras to raise the score to Ulster 20 Castres 3.

Castres spent the five minutes leading up to the half-hour mark camped inches from the Ulster line, with stubborn defence keeping them out in the first instance, although an eventual infringement gave them a highly bankable scrum five metres out. The persistent Frenchmen threw everything they could at Ulster, and, finally realising that brute force would not carry them over the line, insightfully changed tack, with an adroitly clipped kick from Bernard collected in the corner and grounded by Marc Andreu. Teulet converted to reduce the deficit to 10 points, although Jackson had time to add a third penalty just before the break.

Half-Time Score Ulster 23 Castres 10

Fewer than four minutes of the second half had elapsed before Marshall doubled his personal tally, thanks to yet another piece of opportunistic improvisation. The diminutive scrum-half picked up from the maul metres from the line and carved his way to the score with a series of trademark twists and turns. Jackson's conversion was off-target, but he was on hand to atone for the miss moments later with a long-distance penalty which elevated the scoreline to Ulster 31 Castres 10.

Castres then enjoyed a rich spell of possession, rewarded on 51 minutes with a try by Marcel Garvey - touched down on the line and no more, under staunch resistance from several Ulster defenders - and duly converted by Teulet. With Tom Court yellow-carded just before the hour for pulling down a maul, Ulster could have been forgiven for sitting back in the interest of damage limitation, but immediately put together one of their most progressive attacks of the encounter, which led to three more points for Jackson's boot.

With Pienaar introduced into the mix on 60 minutes, Ulster continued to press, now in the quest for the fourth-try bonus point, but were twice undone by miscommunication in their own line-out in very promising positions. However an unsavoury tackle on Pienaar - after which prop Yannick Forestier was sinbinned for kicking the ball away on 74 minutes - gave the hosts another opportunity, eventually squandered in the corner with only three minutes remaining.

As the clock hit 80 minutes it looked for all the world that Castres would have the last word as they probed deep in Ulster territory, but a quick turnover put Ulster back in the driving seat. As the breakaway launched, Pienaar took the opportunity to mark his return to the fold in fitting fashion, picking up from Luke Marshall just past halfway and weaving his way past four or five Frenchmen for a stunning individual try. Jackson's conversion brought proceedings to a close, with Ulster now sitting on maximum points before next Friday's Round Two trip to Glasgow.

Full-Time Score Ulster 41 Castres 17

Ulster
(15 - 9) J Payne; T Bowe, D Cave, P Wallace, A Trimble; P Jackson, P Marshall
(1 - 8) T Court, R Best, J Afoa, J Muller (c), D Tuohy, I Henderson, C Henry, M McComish
Replacements (16 - 23) R Herring, C Black, A Macklin, L Stevenson, N McComb, R Pienaar, L Marshall, C Gilroy

Castres
(15 - 9) R Teulet; M Garvey, D Kirkpatrick, S Bai, M Andreu; P Bernard, T Lacrampe
(1 - 8) Y Forestier, M Bonello, M Coetzee, M Rolland (c), R Capo Ortega, P Faasalele, Y Caballero, P Wannenburg
Replacements (16 - 23) M-A Rallier, G Marmoiton, M Lazar, I Tekori, R Kockott, A Classen, P Bonnefond, T Sanchou