Tom Helm's two wickets in successive balls sparked a Derbyshire collapse to bolster Middlesex's hopes of a win on day three of their LV= Insurance County Championship clash at Lord's.

With the visitors 304 for six in mid-afternoon chasing Middlesex's first innings tally of 401, Helm trapped Anuj Dal lbw for 52, ending a stand of 86 for the sixth wicket with Alex Thomson.

Sam Conners was sent on his way for a golden duck next ball after missing a Yorker and with Toby Roland-Jones taking two in three balls in the next over, including Thomson for 45, Middlesex had taken four for nought in nine balls.

Dal and Thomson kept up their impressive games with a wicket apiece after Middlesex went in a second time but Max Holden struck a rapid 68 not out while sharing an unbroken fourth wicket stand of 141 with Robbie White (79 not out) to leave the hosts 201 for three, a lead of 298.

Skipper Tim Murtagh had singled Helm out as the hosts' best bowler 24 hours earlier and he was belatedly to reap the rewards his stints had deserved, making his double strike at a time when Dal and Thomson appeared untroubled and finishing with three for 52 from 25 overs on a slow pitch.

When Josh de Caires, having survived a huge lbw shout first ball, was bowled by Conners four balls into Middlesex's second innings, five wickets had tumbled without a run being scored.

Despite the early setback, Mark Stoneman and first-innings centurion Stephen Eskinazi signalled the intent for quick runs, running hard to turn two into an unlikely three, while the former hooked Suranga Lakmal into the grandstand for six.

Again, it was Dal and Thomson who briefly checked the hosts' progress, Dal trapping Eskinazi lbw, while Thomson induced a rush of blood from Stoneman, whose ugly cross-batted swipe saw him caught by Conners.

Holden though came out bristling with intent, racing to 50 at almost a run a ball and hoisting Thomson into the grandstand in the process.

White, who scored 65 in the first innings, began more circumspectly but twice cleared the ropes himself as Middlesex took control.