Hampshire 301 for 9 (Markram 88, Rossouw 64, Helm 5-71) beat Middlesex (Morgan 41, Abbott 3-36) by 119 runs
Aiden Markram produced a stunning all-round performance as Hampshire made it three wins from three in the Royal London Cup with a 119-run victory over Middlesex.
South African opener Markram, who is warming up for this summer's World Cup, crashed 88 with the bat off 90 balls to help Hampshire to 301 for 9 before his part-time off-spin gathered 3 for 39.
One-day champions Hampshire have defeated Kent, Glamorgan and Middlesex to leap to the top of the South Group.
Middlesex had won the toss and elected to field first under grey skies.
In response, Markram's compatriot Abbott broke through twice in the first five overs of the chase as he had Paul Sterling leg before and then Dawid Malan caught at point by James Fuller.
John Simpson and Eoin Morgan rebuilt with a free-flowing 65-run stand for the third wicket. But Markram entered fresh from his fifty earlier on to forge a collapse - with Simpson, Morgan and Nick Gubbins all falling within six overs.
Simpson was stumped after some fantastic glovework from Tom Alsop. England one-day skipper Morgan was given extra lives when he offered two difficult chances to Rilee Rossouw on the boundary, before picking out Abbott at short fine leg. Gubbins then cut to Sam Northeast and George Scott was castled by Dawson - leaving Middlesex 121 for 6.
Left arm spinner Dawson found Tom Helm skying to Gareth Berg in the ring and then Nathan Sowter caught behind.
Abbott claimed his third wicket when Steve Eskinazi picked out Northeast at mid-wicket before Mason Crane wrapped up the win when Tim Murtagh was bowled.
Middlesex seamer Helm had led the visitors' attack with a five-wicket haul on a used pitch - which had played slightly slower than against Glamorgan on Friday
Alsop went out at a rate of knots, following his 130 not out against Glamorgan, with three sumptuous cut shots to the boundary. But he fell soon after as he chased a wide delivery from Murtagh and was caught behind, before James Vince handed Helm his first with a steepling top edge.
Markram scored a stylish run-a-ball half century in a 58-run stand with Northeast. But Markram and Northeast fell within an over of each other, the former frustratingly misjudging a pull to mid-on and the latter lbw to Nathan Sowter - leaving Hampshire looking below par at 145 for 4.
Rossouw and Dawson steadied and accelerated with an 81-run partnership for the fifth wicket, the South African collected his 32nd List A fifty - from 49 balls.
Dawson was well caught by Murtagh running around to short fine leg off a top edge before Helm returned to cause carnage. The 24-year-old fast bowler ripped through Rossouw and Berg in consecutive balls before completing a stunning four wickets in eight balls with the scalps of Abbott and James Fuller - the latter having smashed a quick-fire 26.
Chris Wood took Hampshire past 300 with a sweetly struck six over square-leg to set their opposition 302 to win.