Tom Lace (143) struck his maiden first-class century, while Billy Godleman hit a career-best 211 not out on Day Three of the Specsavers County Championship game against Glamorgan.
In a record-breaking day for Derbyshire the pair put on 291 runs for the third wicket in Swansea, the highest for any wicket against Glamorgan.
Harvey Hosein ended the day unbeaten on 53, and will resume on Day Four alongside his captain, with Derbyshire 504-4 and leading by 110.
Rain prevented play from starting at Swansea until 2pm on Day Three. When it did, Derbyshire resumed on 221-2, with Godleman unbeaten on 86 and Lace 78 not out.
The pair passed their 150-partnership shortly after play began, before the Derbyshire captain brought up his first red-ball century of the season off 141 balls, including 16 fours.
Lace’s hundred soon followed, coming in 157 balls and including 12 fours, the on-loan batsman fluent as the pair moved their partnership to 281 runs before tea, just 39 runs adrift.
The 21-year-old fell for a career-best 143 when he was acrobatically caught in the deep by Owen Morgan off Graham Wagg.
But Godleman marched on and made it to 150 in 229 balls, striking 19 fours in the process, as he continued to close in on Glamorgan’s first innings lead.
The visitors drew the scores level before Alex Hughes was out lbw to Michael Hogan for 22.
Godleman continued to score with Hosein at the crease and the 50-partnership between the two came from just 47 balls.
The opener brought up his double-hundred in 281 balls, including 23 fours as Derbyshire extended their lead to 90 runs and breaking the record for the highest score by a Derbyshire batsman at Swansea.
He brought up a personal milestone five runs later, when he surpassed his previous first-class high-score of 204 by sweeping Morgan to the boundary in the 110th over.
Hosein passed fifty with the penultimate ball of the day, as Derbyshire closed a day in which they dominated on 504-4, with a lead of 110.
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