Sussex 169 for 4 (Salt 50) lead Middlesex 138 (Wiese 5-26) by 31 runs
David Wiese's second five-wicket haul of the season gave Sussex the upper hand as they steamrollered Middlesex for 138 on the opening day of their County Championship game at Lord's.
Wiese finished with 5 for 26 from 15 overs, ripping through Middlesex's middle order after the home side had opted to bat first.
The South African all-rounder was backed up by fellow seamers Ollie Robinson and Mir Hamza, who shared the rest of the wickets to skittle Middlesex in just 43.4 overs, with wicketkeeper Ben Brown also claiming five dismissals.
Sussex found batting far easier when they replied, with Philip Salt hitting a half-century and Stiaan Van Zyl undefeated on 46 as they advanced to 169 for 4, a lead of 31 runs.
Middlesex's decision to bat looked questionable from the start, with the visiting fast bowlers finding plenty of movement in humid conditions.
Openers Sam Robson and Max Holden survived edges that fell short of the slips before Robson became the first to depart, nudging an outswinger from Robinson into the keeper's gloves.
Nick Gubbins soon followed, caught down the leg side off Hamza, before Wiese turned the screw with consistent spells either side of lunch.
Holden and John Simpson perished to loose drives outside off stump, while Dawid Malan and Stevie Eskinazi were caught behind fishing at good-length deliveries.
Toby Roland-Jones lifted the Middlesex total into three figures with a couple of crisp cover drives to the boundary before becoming the fifth victim of the day for both Wiese and Brown.
Robinson, who took 3 for 50, got in on the act, reducing the home side to 110 for 9 with lbw decisions to remove Ollie Rayner and Ethan Bamber.
James Harris began to play with some freedom, launching Chris Jordan into the grandstand for six as he shared a last-wicket stand of 28 with Tim Murtagh.
But Hamza finished off the innings by claiming the 300th wicket of his first-class career as he bowled Murtagh, leaving Harris unbeaten on 38.
Middlesex's total represented their lowest first-innings score in red-ball cricket since they posted 98 against Worcestershire at the end of the 2015 season.
The visitors quickly set about wiping out the deficit, with Salt going for his shots and using the short boundary on the leg side as he raced towards a brisk 50.
Although they lost Luke Wells, leg before to Murtagh, Harry Finch helped Salt to reach 78 for 1 at tea - only 60 short of the modest Middlesex total.
The evergreen Murtagh gave his side fresh hope, pinning Finch lbw in the first over after tea and then clean bowling Salt.
Laurie Evans, lbw to Harris for 31, was the only other wicket to fall before the close - but by then Sussex had already established a lead and they begin the second day as comfortable favourites.