Middlesex 169 (Holden 50*) and 232 (Eskinazi 60, Malan 70, Archer 5-69, Robinson 4-59) beat Sussex 171 (Harris 4-61) and 175 by 55 runs
If Middlesex's promotion charge turns out to be successful, they will look back on this victory as a season-defining one.
Defeat here would have left them needing to win all of their last four games to have any realistic chance of going up, and after losing their last five wickets this morning for just 20 runs, there was a fear that they had let a good position slip.
Instead, they were resurgent with the ball, and took regular wickets to keep Sussex in check throughout their chase of 231. This was their third win in a row and their fourth in five; while the mid-summer months have been punctuated by a poor T20 Blast campaign, their red-ball form has seen them keep the season alive going into its final month.
The win also highlighted the credentials of Richard Johnson, the interim head coach, who is understood to be one of four or five names on the shortlist to take the job permanently. Despite following on at Northampton last week and being bundled out cheaply in the first innings here, Middlesex have now won all three of his games in charge, and he would be an obvious choice if they choose to promote from within.
Despite the absence of talisman Tim Murtagh, away on international duty for Ireland, the seamers impressed throughout this game on a pitch that both captains considered underprepared. James Harris - who became the first man in either division to reach 50 Championship wickets when he trapped Harry Finch lbw - was the pick, but James Fuller, Ethan Bamber and Steven Finn all played their part; spinner Ollie Rayner didn't bowl a single over.
Fuller's seven-over spell either side of lunch proved match-winning. Brought to the club primarily as a white-ball bowler, Fuller missed the second half of last season and three months of this with a long-term injury, and his comeback in the T20 Blast saw him leak runs.
But throughout this game he bowled with pace and purpose, and his delivery on the stroke of lunch that found the edge of Phil Salt's bat was a beauty that seamed away off the pitch. After the interval, he had Tom Haines caught by Dawid Malan at point, and when Luke Wright was bowled by Finn for the first pair of his career, Sussex were reeling at 59 for 4.
Finch and Ben Brown both fought hard, but this was a pitch with variable bounce that no batsman ever looked settled on. Danny Briggs and David Wiese frustrated Middlesex with a last-wicket stand of 47, but that their partnership was the highest of the innings suggested that any hope that wicket had flattened out was misguided.
"It was always going to be a tough run chase," Brown said, "and I'm not too disappointed with the way we batted. It was one of those pitches where the ball was rolling along the floor at times, and nipping around.
"A couple of things didn't quite go our way yesterday, and they batted well, so I'm not too disappointed - we'd won four games in a row, and I'm happy with the way we've played our cricket."
Malan's captaincy was another important factor in the win, as he recognised that plugging boundary options by setting defensive fields would deny Sussex the chance to get their chase off to a flier. "If guys are only getting two singles an over, it keeps you in the game," Malan said, "and on a wicket like this, the more balls you can bowl at someone the better."
Salt's uncharacteristically subdued 20 highlighted that best: his early attacking shots only brought singles, and when he reigned that aggression in, the battle was half-won.
Middlesex's overnight score of 210 for 5 looked as though it had set the game up for Malan and Harris to take them to a lead of at least 250 this morning, but they added just 22 before being bowled out.
Due five overs after the start of play, the new ball looked certain to hold the key for Sussex in the morning session, but by the time in was taken, the damage had been done: Malan was caught behind off Ollie Robinson, and Fuller wafted at one outside his off stump which found his edge.
Jofra Archer cleaned up the tail to leave 231 required, but in Brown's mind, the damage had already been done when his side let things slip will the ball yesterday evening.