Derbyshire 227 for 6 (Critchley 87*, Bamber 3-35) trail Middlesex 423 (Robson 134, Holden 119*, Palladino 4-92) by 196 runs
Max Holden completed a maiden first-class century in Middlesex colours on a day when he and another of the county's bright young things shone against Derbyshire at Lord's.
Holden made an unbeaten 119 and helped rewrite the Middlesex record books in the process before Ethan Bamber took centre-stage with three wickets to reduce Derbyshire to 62 for 4 in reply.
Matt Critchley, however, stood firm reaching an entertaining 87 not out as they rallied to 222-6 at the close, 201 behind.
Middlesex centuries are it seems like London buses - you wait four months for one to come and then two arrive at once....
Just 24 hours after Sam Robson became the county's first red-ball centurion since May 6, Holden matched the feat.
However, there were many nervous moments before the former England U19 skipper passed the landmark.
Holden began the day 96 not out, and had added two more when Bamber edged Lockie Ferguson to second slip, bringing last man Tim Murtagh to the crease.
Two swings of the bat later, rain intervened for 20 minutes before play resumed with Murtagh having three more deliveries to negotiate. The seamer survived to thunderous applause, before Holden caressed a cover-drive to the fence to reach his milestone in the following over.
Freed of any sense of responsibility Murtagh (39) launched Ferguson for four boundaries in an over as he and Holden added 66, breaking a Middlesex record for the 10th wicket against Derbyshire which had stood since 1933.
Inspired by his 39 with the willow Murtagh then broke Derbyshire's opening partnership before lunch, getting Luis Reece LBW, though replays suggested the ball pitched outside leg-stump.
The first hour of the afternoon session also belonged to the hosts with James Harris trapping Wayne Madsen LBW shortly after the batsman had reached 11000 first-class runs.
Then it was Bamber's turn to steal the spotlight with two wickets in three balls. The teenage seamer, who only made his County Championship debut last month, plucked out Alex Hughes' off-stump before moving one into the pads of wicketkeeper Harvey Hosein, trapping him in front.
Derbyshire were reeling, but Critchley led the fightback. Aggressive from the off, the spinning all-rounder made the lion's share of a 65-stand with Billy Godleman.
Martin Anderson removed the obdurate former Seaxe for 28, caught at slip, but Critchley moved to 50 in just 54 balls with eight fours shortly after tea having found another ally in the shape of Gary Wilson.
The pair added 60 and were guiding Derbyshire to safe waters when Wilson (31) inexplicably swung across the line at a straight one from Bamber and was plumb lbw.
Bad light delayed proceedings for 40 minutes shortly afterwards, but just before play was due to be abandoned the players returned to controversy when Murtagh thought he'd had Anuj Dal caught at slip for 5, but the batsman stood his ground and the ball was adjudged not to have carried.
Scare survived he and Critchley eased to the close and need just 52 more in the morning to avoid the follow-on.