GJ van Velze's first half try made the difference, and with Tommy Bowe suffering what appeared a serious ligament injury, Ulster will need to regroup as they enter the crucial festive period, with league derbies against Leinster and Munster following in quick succession.

With a point to prove after leaking four tries at home last Friday, Northampton made much the brighter start.

An overthrow at a fifth minute Ulster lineout put them under extreme pressure, from which they were fortunate to escape with only a three-point concession after Stephen Myler's central penalty.

However, the strength of the Ulster pack was soon to tell. A turnover at a ninth minute Northampton maul led to a promising left wing raid which only broke down metres from the line courtesy of a dropped ball from Andrew Trimble,
who was making his 50th tournament appearance.

Superior communication at the lineout was instrumental in Saints' next big surge, but the alert Ulster defence soaked up several minutes of pressure before clearing downfield.

Northampton came straight back, however, and this time number 8 van Velze forced his way over the whitewash wide out on the right after pinpoint passing between the English backs. Myler's conversion made it 10-0 with 20 minutes gone.

Then a smart charge down from Nick Williams on halfway, followed by strong ball-carrying from Rory Best, raised the Ravenhill decibel level several notches.

Jackson duly kicked his first points of the match from the Northampton 22 on the half hour mark, bringing his tally for this season's Heineken Cup to 43.

This was followed by a second break from deep by Williams and despite great acceleration onto the pass from Bowe, another subsequent knock on at the crucial stage stymied the attack.

Jackson failed to claim another three points with a marginally wide penalty attempt, but the young out-half atoned for the miss three minutes later as Ulster turned the screw in the lead-up to the break.

With Tom Court pinching possession straight from Jackson's restart, Ulster were first to probe in the second period. Two minutes in, another infringement saw Jackson slot over from the 22 to close the gap to 10-9.

Northampton, putting on a much more dynamic display than they had eight days before, increased the intensity over the next six minutes.

Jim Mallinder's charges dominated possession and territory as the match reached the 50-minute mark, and only just ran out of terrain in two successive attacks on either flank.

Then the tide turned momentarily as Trimble expertly claimed a high ball, and withstood several challenges before referee Nigel Owens blew for a high tackle on the winger.

With the ball lying in Ulster's half, Ruan Pienaar assumed kicking duties but watched his long range attempt fall narrowly short of the posts.

Craig Gilroy and Paul Marshall replaced Trimble and Jackson on the hour mark, and moments later television match official Derek Bevan was called into action as the Ulster forwards piled over the line after good play at the line-out.

Flanker Williams was unable to force his way over though and the opportunity went a-begging as Ulster infringed at the subsequent five-metre scrum.

Gilroy soon made his presence felt with a penetrating run which cut through the Northampton midfield, but another handling error, this time from Williams, ruined the move a handful of passes later.

Then, as Myler shaped to attempt a drop goal at the other end with the clock moving into the final 10 minutes, Pienaar charged the kick down and launched a fine counter attack with replacement Luke Marshall in support.

Ulster moved upfield at pace, but again were unfortunate as Jared Payne was pulled up for holding on to the ball too long in the tackle inside the Northampton 22.

With three minutes remaining, Paul Marshall made a trademark surge from the base of a scrum as he sprinted over halfway and linked neatly with Bowe. But the winger injured himself as he tried to avoid a tackle and had to be stretchered off with what looked a serious leg injury.

That very attack earned a kickable penalty for the province. Up stepped South African Pienaar but his right-sided kick went wide of the left hand post in what was the final scoring opportunity of a tight encounter.

Northampton then slowed play down to the final whistle and Ulster had to settle for a losing bonus point which sees them stay top of Pool 4 with 15 points from four matches played.