Nick Browne rediscovered the form that brought him five centuries last season as he anchored Essex’s innings at Chelmsford.
Browne’s unbeaten 154 was not only his highest first-class score but it also more than doubled the 150 runs he had managed from seven previous innings.
The opener equalled his previous best of 151 not out at Leicester last year with a straight drive off Shiv Thakor after more than six hours at the crease.
At that point he had batted for 293 balls with 23 fours.
His sterling effort put the Specsavers County Championship Division Two leaders in a strong position to dictate the course of this match.
The left-hander was particularly strong off his legs and was textbook-style in his straight-driving. But he did allow himself one extravagant shot, pulling Thakor through midwicket when he was well past his ton.
Browne gave one chance during his knock, and that in reaching his half-century off 78 balls. Chesney Hughes at slip got a hand to an edge, but could not stop the ball speeding to the ropes for Brown’s 11th boundary.
He had faced another 125 balls when he punched Madsen through the covers to reach a century that included a further seven fours.
The 25-year-old put on 111 in 41 overs with Ravi Bopara, their third-wicket partnership ending two balls after Browne passed three-figures.
Bopara finished one short of a second half-century of the season when he was lbw to Thakor.
Derbyshire took up the option of an uncontested toss and elected to bowl. It seemed a puzzling decision at the time, and by stumps it looked even more debateable.
Essex started serenely with Browne and Jaik Mickleburgh putting on 61 runs in 19 overs before Tony Palladino took the first of two wickets in three balls.
Mickleburgh was given a life on four when Matt Critchley spilled a decent chance at point. And he had added another 20 runs before being trapped to one high on his pads.
He was followed by the in-form Tom Westley, who had scored 432 runs in his previous six Championship innings this year. He lasted three balls, without scoring, before he was pinned in his crease by a ball that swung in to him.
It was an untimely duck as England batting coach Mark Ramprakash had travelled to Chelmsford specifically to check up on him.
Derbyshire’s seam attack toiled but still restricted Essex to just 80 runs in an afternoon session that was alleviated by the introduction of spinners Critchley and Wes Madsen.
Browne greeted Critchley’s arrival by rocking on to his back foot to punch another boundary through the offside.
And Bopara punished the 19-year-old leg-spinner by thumping a wayward full-toss for four.
If Essex had been reliant on boundaries in the first two sessions, Daniel Lawrence had Browne scampering singles, twos and threes as the Derbyshire visibly wilted in the field. Browne, however, still looked spritely.
The giant Anguillan Hughes missed his second chance of the day when he was slow to react to Lawrence’s steepling miscue that landed two feet beyond him at midwicket. By the end the miss had cost Derbyshire 30 additional runs from Lawrence’s bat, including one sumptuous on-drive for four off Palladino.
Lawrence also made it to fifty by the close, by which time the fourth-wicket stand was worth 103.