Skipper Simon Harmer had a night to remember as Essex Eagles boosted their hopes of progress in the Vitality Blast with a 100-runs thrashing of Sussex Sharks at Hove.

Harmer plundered 31 off the final over bowled by Henry Crocombe, who announced on Wednesday that he is joining Surrey at the end of the season, to help swell Essex’s total to 204 for 6.

Sam Cook picked up three wickets in the powerplay on his way to a career-best 4 for 7 as Sussex slumped to 34 for 5 before Harmer finished with 2 for 16 in four overs of accurate offspin and ran out Danny Briggs by deflecting a straight drive from Tom Alsop onto the non-striker’s stumps.

Sussex were bowled out for 104 in 17.3 overs and have now failed to bat their 20 overs in six of their nine games this season.

At the end of the 17th over Sussex would have been happy to have contained Essex to 141 for 5 on a two-paced pitch. But Crocombe conceded 15 off the 18th and skipper Tymal Mills went for 17 in the 19th as Harmer and Shane Snater upped the ante by hitting 41 off the last nine balls.

After Crocombe bowled a wide at the start of the fateful final over Harmer went 6-4-4-6-6-4, swinging him over the short leg-side boundary for all three sixes. It was the second-highest expensive over by a Sussex bowler in Blast history – only Michael Yardy (34) has conceded more.

Before Harmer’s onslaught Sussex had done a good containing job, although several Essex batters got out when they seemed well set. Michael Pepper helped Charlie Allison add 54 after the early loss of Paul Walter, contributing 47 from 29 balls before he sliced Briggs to backward point.

Allison made 20 but was dropped twice and Luc Benkenstein hit 26 but Harmer and Snater’s onslaught left Sussex utterly deflated and their chances of winning had evaporated at the end of the third over when they were 19 for 3.

Cook picked up both openers Harrison Ward and Dan Hughes to catches on the leg-side boundary in his first over then George Thomas was superbly held by Benkenstein trying to clear the wide long-on boundary.

Cook and Snater bowled nine dot balls in a row after the fall of the third wicket to turn the screw and Cook had his third wicket when John Simpson was caught in the covers. Seamer Mackenzie Jones, making his first appearance of the season, removed Oli Carter and Jack Carson.

Harmer was on a hat-trick after he took a fine running catch off his own bowling to remove Alsop, who top scored with 35 for a Sussex team who have now lost seven of their nine games.