It was their heaviest defeat of Derbyshire in terms of runs, beating their win by 169 runs in 1933. It was also their fourth win in as many outings.
With both Warwickshire and Kent winning Sussex needed to maintain their recent impetus. And it was a convincing victory after Derbyshire had batted so resolutely to almost match Sussex in the first innings.
Ultimately, Derbyshire were overpowered. But they had misfortune too. Already without Ravi Rampaul, who left the field on the first day with breathing difficulties and did not return – so Sussex needed just nine wickets for victory - they also lost the services of opening batsmen Ben Slater just before lunch.
Slater was struck on the head by a short delivery from Jofra Archer and retired with concussion. He was later replaced in the batting line-up by Anuj Dal. Dal had appeared in nine T20 matches for Derbyshire this season but this was his first-class debut.
Derbyshire had resumed on six without loss, requiring a further and unlikely 399 for victory. The worn pitch was still playing well and opening batsmen Billy Godleman and Slater suggested that survival, at least, was possible.
Slater square-drove David Wiese to raise the side’s fifty in the 15th over of the morning. Derbyshire looked so comfortable that it was surprising when, in Wiese’s next over, he flattened Godleman’s leg stump.
In the following over Chris Jordan, in the middle of his best spell of the match from the Cromwell Road end, had Wayne Madsen lbw with one that nipped back into the batsman. That made it 59 for two in the 25th over. It was just before and after lunch that the match swung decisively against Derbyshire.
First there was the blow suffered by Slater. And then, after the interval, Sussex too three wickets in five overs. With the second ball of the afternoon session Danny Briggs had Sean Ervine lbw. Three overs later Matt Critchley edged Archer to the keeper and then Daryn Smit played across the line to Briggs and was lbw to make it 89 for five.
It was at this point that Dal came to the wicket. But by now Sussex had gathered a winning momentum. Ollie Robinson replaced Archer at the north end of the ground at 105 for five and with his third ball he moved one away from Alex Hughes to have him caught behind. Robinson dismissed Hardus Viljoen in similar fashion at 140.
The match was completed shortly after tea. In the first over after the interval Dal was lbw to Briggs and three overs later Lockie Ferguson chopped Archer on to his stumps.
Sussex coach Jason Gillespie said: “I thought we were excellent in this game. Scoring those runs early on say one, after being put in to bat with overhead conditions, and the lights on all day, I thought it was a really good effort to get 440.
“We weren’t at our best with the ball in their first innings but then we had that special partnership at the start of our second innings between Phil Salt and Luke Wells. Salt’s innings was pretty special and it bought us time. The match could have potentially been heading towards a draw until then. We scored at six an over, which is virtually unheard of in first-class cricket.”