Northamptonshire 166 for 3 (Willey 100, Beer 2-24) beat Sussex 165 for 7 (Nash 53, Jayawardene 50, Willey 3-27) by seven wickets

If stardom is about taking your moments then David Willey surely has a chance at stardom. He turned Northamptonshire's quarter-final against Sussex into a rout, striking the fastest century of the season in the NatWest Blast - and the eighth fastest of all time - to secure victory by seven wickets with four overs to spare.

Willey reached his hundred in 40 balls. He was out to the next, caught in the deep at midwicket by George Bailey, 10 sixes and seven fours to his name. You can study the wagon wheel if you wish, or you can just take it as read that all the spokes were roughly in the same place. If stardom lands one invitingly in his arc, and the wind is with him, he will probably flay it over midwicket and take the plaudits.

This was a performance to awaken the IPL, one produced by a player who made his England limited-overs debut earlier this summer. But Willey, like his father, the former England allrounder and umpire Peter, does not gush to order: quite the contrary. Invited for his comments in the dugout by Sky TV with the match not yet settled, he gave the impression he regarded it as an imposition.

"Got a decent bat," he said, plugging the make. "Managed to get hold of a few." Deadpan, possibly techy. But he did mention a few beers in Brighton later when one imagined he would celebrate at the right time. Old-fashioned convictions. And no worse for that.

After the match, he was relaxed and happy. "I started quite slowly and didn't pick up the pace of the wicket but I used the wind and the short boundaries to my advantage," he said. "The guys know if I stand still and give myself a chance the boundaries aren't always big enough."

So Northants go to Finals Day. They are increasingly debt-ridden, have asked the ECB for an emergency loan and Willey is bound to leave at the end of the season: perhaps more players besides. Yorkshire, desperate to stretch their Championship domination into T20 are among the leading suitors. Northants' pre-match chats have included lots of chats about the need for strength in adversity. Willey certainly showed that.

Michael Yardy, Sussex's former England one-day allrounder, suffered the headline over, although to be fair to him there was ample carnage elsewhere. He has announced his retirement at the end of the season, but he might feel like retiring forthwith after Willey swung him for 34 from an over, five sixes and a flat midwicket four off the second ball which fell short by two yards. It was the ninth of the Northants chase and, by the end of it, they needed 54 from 11 with nine wickets in hand. Game over.

It was as if Willey said, whether Yardy bowled his left-arm slows over or round: "I know you don't spin it, I see no guile, you are in my arc, you are disappearing many a mile."

Predictably, Willey went to his century in the next over, one of the largest hits of all, Tymal Mills, the fastest of Sussex's attack, disappearing into the crowd at deep square. Mills also conceded three sixes, but dismissed Willey with his next ball, George Bailey catching, for once no grin to be seen.

Willey's record-breaking hundred surpassed Brendon McCullum's 42-ball effort for Birmingham Bears against Derbyshire at Edgbaston earlier this season.

Willey launched his onslaught in the third over when he took 18 off England team-mate Chris Jordan, who was playing his first competitive game after two months out with a side strain. He lost opening partner Richard Levi in the eighth over when Levi, who had struck Chris Liddle for two sixes in the previous over, was leg before to the first ball from legspinner Will Beer after they had put on 78.

Northants have reached Finals Day for the third time, and Willey will have fond memories of their title triumph in 2013 when he first shot to prominence with a matchwinning performance with bat and ball and enjoyed a run-in with Surrey's Jade Dernbach along the way.

With Willey fit again after missing several weeks earlier in the season with an ankle ligament injury, Northants will feel anything is possible when they return to Edgbaston on August 29.

Sussex must have imagined a quite different outcome when they were 97 for 2 midway through their 20 overs. But Mahela Jayawardene's silky half-century had just come to an end - his scoop off a full toss from Azharullah stunningly caught by Josh Cobb running around the fine leg boundary - and Sussex's innings immediately declined. Chris Nash, the mainstay, was leg before in the 13th over for 53, hitting across the line at Rory Kleinveldt. Only 67 runs came in the second phase - no wonder Sussex prefer to chase at Hove

One of those responsible was Willey, one of two reliable death bowlers in Northants' line-up, the veteran Azharullah being the other. Willey returned 3 for 27 with the ball as well. Luke Wright, the Sussex captain who had done so much to plan their progress to the quarter-finals, had fallen third ball for nought and, for good measure, he added Jordan at mid-off - another facet of a malfunctioning return - and Will Beer, undone by a slower bouncer.

Willey's bowling possessed variety, his batting was predominantly a succession of leg-side swings but Hove's tight square boundaries, his excellent eye, and a bat kindly provided by the makers who will remain anonymous (no point cheapening a record, after all) did the rest.

"We were hoping to be 180, but that catch by Cobb changed the innings, we were playing beautifully at the time," said Wright. "That innings was pretty special. Everybody else made it look like hard work. That innings was pretty special. It was like watching Gayle bat. If we could have had fielders standing in the middle of Hove we might have had an answer to him."