Ian Ward scored a superb maiden hundred for his new county but Sussex still have a testing day ahead of them if they are to save their Championship match at Northampton.

The left-hander has already scored 82 against Surrey in the Championship opener and three successive one-day fifties this season and how Sussex were grateful that he maintained that form with 115 as Northamptonshire's two off-spinners, Jason Brown and Graeme Swann, turned the screw on Day 3.

At 96-4 even Sussex's first target of 251 to avoid the follow-on looked some way off but Robin Martin-Jenkins joined Ward to put together a crucial partnership of 87 in 30 overs before Matt Prior led some spirited counter-attacking by the lower order. Sussex were bowled out for 294 to concede a first innings lead of 106.

In three overs before the close Northants had made 6-0 in their second innings and lead by 112 going into the final day.

Brown and Swann needed little encouragement on a pitch giving them plenty of help, but this was Ward's day. Already, in a month with his new county, he has shown himself to be a batsman with no obvious weakness and yesterday he looked a class apart when Brown and Swann began to probe for weaknesses.

Ward punished anything short and was equally at ease using his crease to smother the spin or trying to hit them off their length with punishing drives between square and mid-wicket.

He reached his half-century in the last over before lunch and after that his first hundred for the county was never in doubt.

A textbook extra cover drive and pulled six over mid-wicket off successive balls from Ben Phillips, the pick of the Northants' seamers, took him to 99 and he reached his 18th first-class hundred in the next over.

So it was a surprise when he fell eight overs before tea, well caught by Johann Louw when he dragged a slog-sweep off Swann aimed at mid-wicket down to the square leg boundary. He had batted for three hours 46 minutes, faced 202 balls and hit ten fours.

Martin-Jenkins provided crucial support although it's unlikely any of his previous 20 first-class fifties contained, as this one did, just a single boundary.

Martin-Jenkins, whose 51 came off 150 balls, was sixth out at 231 when he edged Brown's arm ball to slip and Sussex were still four runs short of the follow-on target when Prior was caught off the back of his bat as he swept Swann out of the rough.

Prior was not the only Sussex player who must have run over a black cat on his way to the ground. Richard Montgomerie turned a ball in Brown's first over into Michael Powell's shin pads at short leg which rebounded into the grateful hands of slip. And Mohammad Akram looked on the end of a poor decision by ICC panel umpire Neil Mallender when run out.

Northants have arguably the weakest seam attack in the first division and their survival prospects depend heavily on the ability of Swann and Brown to make the most of the country's most spin-friendly pitches.

Brown also claimed the wickets of Murray Goodwin who was bowled through the gate, and Mark Davis, leg before when replays suggested he was outside the line, while Swann had Chris Adams stumped and Tim Ambrose, who top-edged to slip sweeping.

Sussex crept past the follow-on target eight down and their last two wickets added another 43 runs and, just as crucially, occupied nine overs as Akram and Mushtaq took liberties against Brown and Swann and forced David Sales to bring back his seamers.