Joe Denly just missed out on a century as Middlesex beat Yorkshire Bank 40 rivals by nine wickets at Southend.
The former England opener was left stranded just shy of three figures when he thrashed Michael O'Shea to the rope to bring up the winning runs with 12.1 overs to spare.
Dawid Malan, who had hit the previous ball for three, was also unbeaten on 58 as Middlesex coasted past the Unicorns' 170 all out.
Tim Murtagh and Tom Helm did the majority of the damage with the ball, grabbing three wickets apiece, with only opener Matt Lineker's 53 giving the Unicorns hope of notching a first win of the campaign.
Devon Endersby removed Paul Stirling in the first over of Middlesex's response
to give the hosts belief but from then on Denly took over as he hit eight fours and four sixes in his 86 balls.
After Murtagh initially removed Tom Lancefield, Lineker and O'Shea put on 56 for the second wicket.
But when O'Shea was run out by Helm, with the score on 91, a procession of wickets fell thereafter to leave the Unicorns short.
Helm removed the middle order, on his way to figures of 3-27 from his eight overs, while Murtagh returned to prise out the tail and return 3-35.
Stirling began the chase by crashing Endersby's second ball to the rope but he was on his way next up after offering a catch to Luke Beaven.
Denly strode to the crease with the score on four, but took control to leave Middlesex two points adrift of Group C leaders Somerset.