A masterclass from Moeen then, 121 not out from 60 balls with eight fours and 11 sixes. Essex, Notts and Worcestershire safely in for Finals Day, join us tomorrow to find out if it will be Gloucestershire or Derbyshire joining them on 21 September. Cheerio now.
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Another remarkable night and Adam Williams will recap it all for you with his match report here, that will later include the highlights from Hove. Watch how the ball sailed into the night sky and frequently out of the ground.
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And we've still got one more quarter-final to come on Saturday.
We're off to Bristol as Gloucestershire host Derbyshire.
Derbyshire are the only county to have never reached T20 Finals Day so will be hoping to make a bit of history, but an exciting Gloucestershire side, who finished second in the South Group stand in their way.
We'll have full coverage for you across BBC Sport with live radio, text and in-play highlights.
In his last four T20 innings he has made 280 runs.
Moeen made 13 runs in four Test innings just a few weeks ago, with ducks against Ireland and Australia.
Just as Ravi Bopara did for Essex on Wednesday and Alex Hales did for Notts last night, magical Moeen won it with a six.
Poor old Reece Topley almost pulled off a piece of brilliance on the boundary but his hand touched the ball when his foot was on the rope. The very next ball he had another, much simpler, chance but this happened...
Not your night, David...
Now who is going to try some of these shots in the Saturday leagues tomorrow?...anyone?
Moeen was dropped on five in the second over of the Worcestershire reply by Alex Carey behind the stumps off Ollie Robinson and he certainly made Sussex pay.
But after Salt fell for 72 from 40 balls in the 11th over, Sussex lost Carey and Wiese in the 12th, wild man Wiese here out first ball..and his evening was sadly not about to get any better...
Poor old Phil Salt's superb innings seems a bit overshadowed now, but he helped Sussex to 55-0 after the six powerplay overs and 94-1 after 10.
They used to have huge imitation eggs over the boundaries at Hove when Sussex were sponsored by a local egg company and there were prizes for hitting them. This is the winning strike tonight and the only one of Moeen's 11 maximums that might have hit one of those eggs, some of the others sailed straight out of the ground.
Essex with Bopara, Notts with Hales and Nash, now Worcestershire with Moeen. Finals Day is going to be some watch eh? Keep 21 September free.
More from Luke Wright: "Just incredibly proud, we have had eight out of nine sell outs here which reflects how well we played. Disappointed not to get through, it was an amazing day last year, but we are getting great young players through, we are building."
Sussex skipper Luke Wright on the dropped catch by Alex Carey with Moeen on five: "Carey has got us into the quarter finals there is no blame whatsoever. I take my hat off, I am a massive Mo fan and that was world class."
Moeen Ali: "They got a good score but we thought they'd get 200 at one point so we dragged it back. It's my highest score and in a quarter-final against a top side."
Three quarter-finals and they have all been won with a six. We'll hear from Moeen next.
Moeen was on 109 when this happened...