Sussex celebrated their promotion by completing victory over Northamptonshire by an-innings-and-19-runs with a day to spare at Hove.
The south coast county's return to the top-flight had been confirmed the previous day when they amassed enough bonus points from the fixture to ensure a top two finish in Division Two.
And, by turning their strong overnight position into an eighth win of the season, Sussex moved to the brink of clinching the Division Two title.
They will be confirmed as champions of the lower tier with a game to spare if Glamorgan fail to beat Surrey in a match that is due to finish on Friday.
Northants resumed on the third morning at 48-2 in their second innings, requiring another 208 to make Sussex bat again.
Despite the best efforts of opening batsman Mal Loye (73) they failed to do so, home seamer Yasir Arafat finishing with 5-74 - taking his match tally to nine wickets - as Northants were all out for 237 in mid-afternoon.
Sussex have secured an instant return to the top-flight after they collected the required amount of bonus points on day two of their match with Northamptonshire at Hove.
Sussex began the tie needing eight points to ensure a swift return to Division One following their relegation last season.
But Worcestershire's failure to secure maximum batting points against Middlesex cut that target to seven, and they surpassed the required amount during a second successive day of dominance against Northants.
Resuming the day on 236-2 - some 111 runs ahead of the visitors, Sussex piled on the runs as Chris Nash posted 169 to take the score past 300.
And promotion was sealed when eighth-wicket pair Yasir Arafat and Ollie Rayner took them beyond the crucial 350-run mark shortly after lunch.
Sussex were eventually dismissed for 381, Jack Brooks the pick of the Northants attack with figures of 4-88.
Resuming their second inning some 255 runs away from making their hosts bat again, Northants lost opener Stephen Peters (22) and Alex Wakely (8) to Yasir Arafat before stumps.
Sussex look set to secure promotion with a game to spare after bowling out Northamptonshire for just 125.
Sussex openers Chris Nash and Michael Thornely had no such trouble with the pitch, however, as they launched the reply with a 228-run partnership in 44 overs.
Thornely, dropped at second slip on 24, made the most of his reprieve to hit 11 fours and a six as he compiled a career-best 89 before he was bowled by Jack Brooks, who also picked up nightwatchman James Anyon just before stumps.
Nash was utterly dominant as he scored his third century in five games, ending the day unbeaten on 122 (14 fours, five sixes) with Sussex already 111 in front on 236 for two.
The visitors had produced some pitiful batting earlier in the day with only wicketkeeper David Murphy, who top scored with 47, providing any real resistance as they were dismissed in 46 overs. Extras was the next highest score with 16.
Pakistan paceman Yasir Arafat bowled three of his four victims, while seamer Anyon, who extracted extra lift in a hostile eight-over spell down the slope, took three wickets.
Sussex need just eight points to secure an immediate return to Division One.