In doing so they made it a double over Sussex having beaten them by an innings and 120 runs in Northampton earlier in the month.
At the start of play on the last day the main question was whether the match would survive until lunch. But lunch was still a long way away when Northants crossed the line, mainly because of an aggressive and unbeaten 47 from 43 balls from Saif Zaib, who had shown his liking for the Sussex bowling in the earlier match, but also because of Keogh, who made 60 not out from 112 deliveries.
Northants resumed on 131 for two, with Luke Procter 47 not out and Keogh unbeaten on 24. They needed another 87 for victory.
The odds were always against a young and inexperienced Sussex side, particularly on a pitch that appeared to flatten out as the match progressed. And batting conditions were never more benign than on the fourth morning, when there was hardly a cloud in the sky.
Sussex opened up with Delray Rawlins’ left-arm spin from the sea end and the bouncy pace of Jamie Atkins. Procter reached his fifty when he worked Rawlins through midwicket for two. He had faced 149 balls and hit five fours. But he had added just one run to his score when he was out, flailing at a wide delivery from Atkins for Aaron Thomason to take a good catch low down at first slip.
The Sussex team did well to celebrate the wicket because it was to be their only success of the morning. But this young and inexperienced side did well to keep the match in the balance until the final hour of the third day, when Procter and Keogh moved the match decisively in the direction of Northants.
The game ended with a flurry of blows, mostly from Zaib, who showed his intentions when he took a step down the wicket and clouted Rawlins over wide mid-on for six. There was another six, and also five fours.
Sussex captain Ben Brown: “It was frustrating again. There were highs and lows and we played well in patches. And we kept in the game. But in the end Northants were the better side and their experience showed over the four days.
“We struggled at the front part and the last part. We lost eight wickets early in our first innings. And I think their target of 218 should have been more challenging for them. It doesn’t get any easier – we’re playing Yorkshire next week. But there are good things to look back on. Tom Haines scored a fantastic hundred and it was encouraging to see Jamie Atkins running in and really smashing the pitch.
“It’s a young and inexperienced side, which is challenging at times. But the spirit and commitment is excellent. I can’t ask for anything more from the team. At times it’s a case of them trying too hard.”