Indeed, Castres had the chance to kick the ball dead but elected to play on past the 80th minute, and they paid the price for that decision in the end.

Ulster won a last-gasp turnover in their 22, thanks to Jared Payne, and launched Luke Marshall into space on the right. Fellow replacement Ruan Pienaar provided the support, collecting the youngster's pass and brilliantly breezing past two defenders on the way to the try-line.

Paddy Jackson converted to complete his 21-point haul as last season's Heineken Cup runners-up celebrated what could turn out to be a crucial bonus point.

Castres had taken a fifth minute lead at Ravenhill, their full-back Romain Teulet splitting the posts with a 40-metre penalty from the left after Ulster had infringed at a maul.

Jackson had the Ulstermen level soon after, a half break from Darren Cave getting them into scoring range and the young out-half converted from in front of the posts.

Paul Marshall's accurate box kicking was an early feature for the hosts, who were forced into a late change as back injury victim Stephen Ferris made way for Mike McComish.

They ten swooped on a loose Pierre Bernard kick to notch their first try. Jared Payne gathered the ball and darted through a gap, showing great awareness to put Andrew Trimble away for the left corner with a perfectly-timed pass.

A superb touchline conversion followed from Jackson and soon after Bernard missed a good chance to reply, swinging a penalty effort to the left and wide.

Jackson stretched Ulster's lead to 13-3 following a storming attack involving backs and forwards. Despite being brought to ground, the out-half linked with Paul Marshall before John Afoa sent Dan Tuohy tearing down the left.

Ulster were becoming rampant at this point and it took a textbook wrap tackle from Marc Andreu to knock the advancing Tommy Bowe in touch, with Marshall's distribution skills again to the fore.

From a Chris Henry turnover in midfield, Marshall spotted his opportunity. The quick-witted scrum half chipped over the top and won the race to touch down behind the posts. Jackson's conversion made it 20-3.

A bout of solid defending kept the Castres forwards out as they tried to drive over from close range, before Bernard's clever cross-field kick gave Andreu a simple run-in for a try on the left.

Teulet added the extras to halve Ulster's advantage, however an immediate penalty from Jackson and a couple of bone-crunching hits from European debutant Iain Henderson saw the hosts reassert themselves before the break.

The 20-year-old made a strong carry when play resumed as Ulster hunted for their third try. They scored it within three minutes, man-of-the-match Marshall wriggling away from two defenders on a short burst to the line.

Jackson missed the conversion but weighed in with a long range penalty push the province through the 30-point mark.

Castres hit back when Garvey's momentum took his over the line following another spell of French forward grunt. Teulet converted from close range to reduce the arrears to 14 points (31-17).

Tom Court's sin-binning for a maul offence put Ulster under further pressure. With a greater chunk of possession the French outfit were looking dangerous - former Ravenhill favourite Pedrie Wannenburg was certainly putting himself about.

Nonetheless, Jackson's fifth successful penalty of the night kept Ulster on course for an opening night success.

Rory Best was central to a late push for that much-sought after fourth try, but time was running out as Castres defended stoutly, even after having prop Yannick Forestier yellow carded for kicking the ball away.

Misplaced passes and a general lack of invention saw Ulster foiled on a number of occasions. Castres retained the ball well and Garvey threatened from deep as they pressed for a closing score.

But Ulster had the last word in injury-time, rediscovering their clinical touch as the returning Pienaar, such a driving force during last season's successful campaign, showed his class once again on the European stage.