David Sales condemned Sussex to another day of hard labour with his first century since taking over as captain of Northamptonshire.

The Sussex bowlers must have sensed what was coming when Chris Adams lost his fourth toss out of six and although they took three wickets with the new ball, Sales and Usman Afzaal soon began to put ideal batting conditions into perspective.

They added 181 in 64 overs for the fourth wicket with Sales making unflustered progress towards three figures while his more watchful partner dug in to frustrate Sussex again, three weeks after he had scored a century against them at Northampton.

Afzaal had an inexplicable lapse in concentration on 69 which cost him his wicket, but Sales never looked like getting out.

He will resume today on 153 with the visitors 315-5 and Sussex needing wickets this morning with a new ball which is only ten overs old.

It was another frustrating day for the champions who urgently need a win to give their season some momentum.

The newsletter the club produces for home matches summed up the mood nicely.

The only comfort it could glean from last week's run-feast against Warwickshire was that Sussex picked up sufficient points from the draw to keep them off the bottom of the first division table.

They bowled with commendable discipline yesterday which was just as well on such an easy-paced pitch and even when Sales and Afzaal were together the run rate never got much above three an over.

Sales was being groomed for international cricket, but he suffered a severe knee injury on the England A tour of the West Indies in 2001 when Sussex's director of cricket Peter Moores was coach and Ian Ward among his team-mates.

He is probably well down the England pecking order now, but his ability has never been in doubt while a record that includes four double-hundreds and one score of 300 suggests he relishes making bowlers toil long and hard.

Sales came to the crease yesterday with his side facing a mini-crisis after they had lost three wickets to the new ball in the first 17 overs.

James Kirtley claimed his first Championship scalp at Hove since the end of last July when he surprised Tim Roberts with extra bounce and Sussex had a real spring in their step after Robin Martin-Jenkins took two wickets in eight balls.

An outswinger followed by a ball which nipped back into his pads undid Tom Huggins and rewarded a clever piece of bowling while Martin van Jaarsveld lost his middle stump, bowled through the gate by another delivery seaming into the right-hander.

Martin-Jenkins took 2-16 in eight pre-lunch overs, and it was a surprise that he was used so sparingly after lunch as Adams gave Mushtaq and Mark Davis long spells in tandem.

Apart from an inside edge which went to the boundary, Sales hardly played a false shot, reaching his hundred in the first over after tea.

Generating most of his power through a strong bottom hand, he had collected 20 fours and two sixes by the close, the second an outrageous cut over backward point for six off James Kirtley to reach 150.

Kirtley's rueful grin suggested it is an area where he is infrequently deposited.

If Sales had ordered Afzaal to play the anchor role he couldn't accuse him of disobeying orders.

The left-hander laboured dilligently for four hours over his runs with four boundaries and two sixes, both off Mushtaq.

The second was pulled over the short mid-wicket boundary and out of the ground, but Afzaal got under the shot when he attempted a repeat with the replacement ball and Murray Goodwin pouched a well-judged skier.

No wonder Mushtaq stood arms aloft, offering a silent prayer to the heavens. It was that sort of day for Sussex.

Jeff Cook followed three overs later, playing back to Davis, but Gerard Brophy, one of three South Africans in Northamptonshire's team, will be with Sales when they resume today although he did have a moment of alarm on 14 when an inside edge off Mushtaq rolled an inch or two past the off stump.