Essex 160 for 5 (Delport 55, Reece 2-24) beat Derbyshire 126 (Harmer 4-19, Nijjar 3-26) by 34 runs

Simon Harmer hadn't had a particularly rewarding Blast season. Unstoppable in the Championship, he had generally become a mere mortal over 20 overs. Then Derbyshire, in their first T20 Finals Day, had to contend with him on a turning Edgbaston pitch and the story changed as his destructive display pointed Essex towards a comprehensive victory and added another satisfying memory to an outstanding summer.

Harmer has been Essex's Championship showstopper: his 78 wickets at 18.12 are the prime reason why they have a title showdown with Somerset at Taunton next week. As Essex's captain in the Blast, however, he had mustered 10 wickets all season and disappeared for nine an over. He was just another player hoping that Edgbaston might look favourably upon him.

All that changed in a second semi-final in which Derbyshire succumbed meekly on a turning surface, falling 34 runs short of Essex's challenging 160 for 5. They didn't play spin particularly well, and a couple of their dismissals could fairly be described as naïve, but when it comes to facing Harmer they are not alone in that charge.

Harmer finished with 4 for 19, his tranquillity never threatened, and he had quite an ally, too, in Aron Nijjar, a 24-year-old left-arm spinner from Romford, who had the onerous task of replacing the modish Australian leggie Adam Zampa on Finals Day in only his second Twenty20 match, conceded 14 runs in his first four balls, but lived to tell a glorious tale as Essex won a T20 semi-final at the fifth attempt.

Harmer and Nijjar took three wickets apiece in the space of 58 balls, five of them hitting the stumps. When the sixth batsman to perish, Alex Hughes, was lured down the pitch by Nijjar and stumped, so fell Derbyshire's top-scorer, on 23. There was another wicket for a spinner, too, when Dan Lawrence bowled Fynn Hudson-Prentice.

Harmer's first ball jolted Derbyshire, their captain, Billy Godleman, the second batsmen to fall as he turned one sharply to hit the left-hander's off stump. He repeated the dose in his third over against Leus du Plooy, another left-hander, another delivery that turned big. Next ball, Anuj Dal, determined to use his feet, ran at one and was bowled through the gate. His last wicket was Daryn Smit, who tried to reverse sweep him past two fielders at backward point, the most befuddled shot of all.

"I'm used to seeing the ball disappear so it's nice to bowl on something that suits me," Harmer said. Essex started their Blast campaign in the South Group so badly that they have essentially been playing knockout cricket for six matches, knowing that one more defeat would be fatal, and the knowledge has improved them.

Nijjar will attract less attention, but his contribution was, in a way, all the more remarkable because he had not bowled a single delivery in Essex 1st XI cricket all season. His last game of note was a 2nd XI match against Hampshire at Southampton in the first week of August. When Wayne Madsen sniffed vulnerability and struck him for 4-6-4 in his first four balls, things looked ominous; for him to then bowl Madsen round his legs, trying to sweep, was a crucial response.

Derbyshire were the last of the 18 counties to reach Finals Day and for all but the most committed follower of county cricket they could hardly have been more of an unknown quantity. Names did not as much trip off the tongue as go clean out of the mind. Obscurity, for a few hours at least, was in vogue. A side that reached the final stages by toppling Lancashire at Old Trafford were clearly capable of being better than the sum of their parts, and they will be deflated by their display.

Essex took command with an opening stand of 78 in 8.1 overs, Cameron Delport the dominant factor. His 55 from 31 balls gave him 408 runs for the tournament and the highest strike rate, at 172.15, of any of the 13 batsmen who had passed that 400-run mark. He might have fallen early, a leg-side swing against Logan van Beek falling safely when he was only 6, but his strokeplay became increasingly daunting until he deposited Hughes to long-off.

Once Delport had been silenced, Derbyshire shook themselves down and gradually got back into the match on a grippy surface that suited their medium-paced mix. Lawrence, who has grown into the T20 format this season by adopting a more aggressive approach, made little impact as he carved Hughes' knuckle ball to third man; Ryan ten Doeschate, lbw to Luis Reece's offcutter, also missed out.

Tom Westley, Delport's opening partner, played the other innings of substance, 39 from 34 balls, although he, too, had fortune on his side, on 13, when van Beek failed to throw him out from mid-on. Westley's departure to Reece at deep backward square leg preceded a problematic finish for Essex as they failed to find the boundary for 37 deliveries, from Ravi Bopara's third-man dab off Reece to Adam Wheater's square drive four balls from the end when Ravi Rampaul narrowly missed his yorker.

Bopara has crabbed all season about batting as a finisher at No. 6, and who found himself up at five for Finals Day. His scoring rate in the closing overs has been spectacular, justifying his place in the order, but it was a more restrained Bopara (28 from 23 balls when a ramp shot went awry) who guided then to 160 for 5. It was easily enough.