Hampshire 295 for 8 (Weatherley 93, Gubbins 62) beat Derbyshire 152 (Guest 44, Kelly 5-19) by 143 runs
Dominic Kelly took Hampshire's first List A hat-trick since 1981 and his first professional five-wicket haul to set up a crushing 143-run victory over Derbyshire in the Metro Bank One Day Cup.
Kelly, the 18-year-old quick, dismissed Zak Chappell, Harry Moore and Daryl Dupavillon to become just the third treble taker for Hampshire - after John Rice against Northamptonshire in 1975 and Malcolm Marshall against Surrey.
Joe Weatherley had put the victory in motion with an authoritative 93 in tandem with Nick Gubbins' 27th format fifty - the pair putting on 113 to set Hampshire towards 295.
Other than Brooke Guest's 44, Derbyshire failed to compete in reply before Kelly's heroics.
Last year's losing finalists Hampshire end their Utilita Bowl games with a 100 percent record, and just one defeat so far to sit pretty for a knockout place. For Derbyshire this was their second loss.
Derbyshire won the toss on their first visit to Utilita Bowl for a decade chose to bowl first, and exercised a great deal of accuracy to hold Hampshire to 32 in the first 10 overs.
Top-order batting hadn't thrived for Hampshire so far in the One Day Cup but each of the top three stole the limelight with a patient display which laid the foundations for a second half of the innings siege of runs.
Fletcha Middleton scored 30 of the first 44 runs, in alliance with Weatherley, before a steepling top-edge gave Daryn Dupavillon his first of three wickets.
But that breakthrough only began a foundation-setting stand of 113 between Weatherley and Nick Gubbins - one that never lacked control, although often felt like the par of 280 was a long distance off.
Weatherley is signed with the Brave during The Hundred, but due to a lack of action has been allowed to feature for Hampshire. Last year he scored 100 and 40 in his two innings, and after just one against Lancashire, used his furlough to rack up the runs.
His innings was a masterclass in seamlessly moving through the gears, with his seventh List A fifty coming in 88 balls, before starting to play more regular shots on his way to 93.
Gubbins seemed to simply tick the runs upwards in his 59-ball half-century as the slow start began to flourish.
The platform allowed wickets to fall regularly, but with runs accompanying. Gubbins was bowled by a stunning dipping yorker by Dupavillon before Tom Prest sliced to backward point.
Weatherley's hundred hunt was ended when he was run out attempting a third run, but Ben Brown came in to thump 31 off 22 balls.
Brown's stay was ended with a slog sweep to deep square, Felix Organ was lbw first ball, Dom Kelly clipped to mid off and Toby Albert holed out to the final ball of the innings - 85 runs had come off the final 10 overs through to get Hampshire to their highest List A total versus Derbyshire.
Table-toppers Derbyshire's reply never truly got going, especially after Luis Reece was adjudged to have been caught behind third ball.
Matt Lamb needed a runner before he was caught off a top edge, before David Lloyd nicked a Brad Wheal snorter behind and Anuj Dal was bowled by Kelly's pace.
However, Brooke Guest was timing the ball exceptionally, in particular back-to-back offside sixes off Felix Organ. But his promise of dominating the run chase was ended after a running mix-up with Samit Patel, with Ross Whiteley picking out deep square leg soon after.
The scene was then set for Kelly to end the 43-year itch, as Chappell swung high into the air, Moore was castled and - after Sam Connors had fallen in the intervening over - Dupavillon was leg before.
