Middlesex 403 for 6 (Robson 136, Higgins 106, Carson 3-89) trail Sussex 554 for 9 dec (Simpson 167, Pujara 129) by 151 runs
Sam Robson and Ryan Higgins continued their fine form with centuries as Middlesex's run-fest of a game with visitors Sussex continued on day three at Lord's.
Robson underpinned the hosts response to Sussex's mammoth 554 for 9 with 136, the 35th first-class hundred of his career, while Higgins added the flair his third century of the campaign - an effort of 106 in Middlesex's total of 403 for 6.
Sussex, for whom Jack Carson returned figures of 3 for 89 will rue dropping Robson twice on 51 and 129, while Higgins was also given a life on 67 - England seamer Ollie Robinson the unlucky bowler on each occasion.
Given Robson's heroics it's important to reflect he may have departed the scene in the opening over of the day. Responding to a call from partner Holden for an injudicious single, the right-hander running to the striker's end would have been gone for all money given a direct hit. It set the tone for some sketchy running by the opener who suffered at least two other close calls.
Robson's driving however, whether square or through the covers was exquisite, one such stroke taking him to his half-century. The landmark came amid a testing morning burst from Robinson, Robson surviving a confident lbw shout from one which was just going over the top before Clark grassed the first of the two chances offered a slip, a tough one, but an expensive miss nonetheless.
At the other end, Max Holden, a man revitalised this season moved to 50 with a minimum of fuss, helped by five boundaries, allowing the pair to steer the hosts to lunch at 140 for 1.
Holden however, as on a few occasions this year fell soon after a resumption when the ball after dancing down the pitch to strike Jack Carson back over his head for four, he flashed at a wide one from the spinner to be caught at slip for 61.
Leus Du Plooy's contribution was brisk but brief, the acting captain paddling an innocuous ball wide of leg stump from Jaden Seales straight down the throat of long leg.
Robson, though, found another ally in the form of all-rounder Higgins, who came out as ever bristling aggression, reverse sweeping Carson for four before playing the shot in the more orthodox fashion for the first six of the innings into the Grandstand.
Robson meanwhile crunched his 14th four through cover to raise his hundred as the stand realised 79 by tea. The opener was given a second life shortly after the restart, Clark again the culprit at slip, Robinson again the unlucky bowler. Clark beat the ground in frustration, but the second top at least didn't prove costly as Robson fell to the new ball, chipping a tired shot straight to mid-wicket.
Higgins continued to be aggressive while Robinson continued to curse his luck. The seamer first found the inside edge of the Zimbabwean's bat only for the ball to trickle onto the stumps without dislodging the bails, before Higgins flashed hard at a wide one on 67 to be reprieved again as James Coles failed to cling on at third slip.
That scare survived, and with the luckless Robinson finally retreating into the outfield, Higgins forged on, striking Coles for successive boundaries to reach his hundred, before dancing down the pitch to Carson and missing the ball to be stumped by John Simpson.
Tom Helm, promoted to seven, fell only two balls later in identical fashion to cause a few nerves, but 20-year-old Nathan Fernandes underlined his promise with a composed unbeaten 50 to leave the hosts just two short of the follow-on figure of 405 at stumps.
