Middlesex 401 and 201 for 3 (White 79*, Holder 68*) lead Derbyshire 304 (Dal 52, Helm 3-52) by 298 runs
Tom Helm's two wickets in successive balls sparked a Derbyshire collapse on day three to bolster Middlesex's hopes of a win in their LV = Insurance County Championship clash at Lord's.
With the visitors 304 for 6 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. Next ball Sam Conners was sent on his way for a golden duck after missing a yorker and with Toby Roland-Jones taking two in three balls in the next over, including Thomson for 45, one shy of his career-best, Middlesex had taken 4 for 0 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 sharing an unbroken fourth wicket stand of 141 with Robbie White (79 not out), his second half century of the game to leave the hosts 298 to the good with a day to go.
Helm, soon to turn 28, has been on England's white-ball radar for a number of years, taking part in training nets as recently as last season. Former England seamer Geoff Arnold has watched Helm a number of times and is known to be a fan, yet injuries and losses of form as well as competition for places has meant he is still shy of 100 first-class wickets.
Skipper Tim Murtagh had singled Helm out as the host's 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 on a benign pitch reminiscent of those in the late noughties and early 2010s here at the home of cricket. His final return of 3 for 52 was the least he deserved for his 25 overs of hard yakka.
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 host's 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. The former England Lion suggested at the back end of last season he was emerging from three lean years and there were plenty of signs of that resurgence here as he raced to 50 at almost a run a ball, hoisting Thomson into the grandstand in the process.
White, who'd been promoted ahead of Holden after his 65 in the first innings, began more circumspectly, but caught the mood, twice clearing the ropes himself in another polished effort, underlining his big leap forward over the last 18 months.