Alex Lees wrote his name into Yorkshire history when he became the youngest player to score a double century for the county on another record-breaking day in the LV= County Championship match against Derbyshire at Chesterfield.
The 20-year-old left-hander was unbeaten on 275 when Andrew Gale declared, the second highest score by a Yorkshire batsman since the Second World War.
Gale and Gary Ballance both contributed fifties to a massive total of 617 for five and at the close Derbyshire were struggling on 94 for five after Steven Patterson and Jack Brooks claimed two wickets apiece.
Lees had gone into the second day on 171 with Yorkshire already in a commanding position but it was Gale who dominated the morning session with some brilliant strokes on both sides of the wicket.
He drove and pulled his way to a 73-ball half-century and hit 13 fours in his 74 before he was bowled sweeping to give 19-year-old off-spinner Peter Burgoyne his first championship wicket.
It was a deserved reward for Burgoyne, who bowled with impressive control, but the stage belonged to Lees. He reached the memorable milestone of a double hundred, from 321 balls with 30 fours, when late cutting the spinner.
At the age of 20 years and 95 days, he is the youngest Yorkshire player to achieve the feat since Richard Blakey, who was 20 years and 225 days when he scored 204 not out against Gloucestershire at Headingley in 1987.
Lees went into lunch on 221 out of 509 for three and there was more punishment to come for the Derbyshire bowlers as Ballance opened his shoulders against his former county.
He hit four sixes before being stumped for 66 giving Wes Durston the charge. There was no shifting Lees, though, and the youngster went to 250 when he edged Durston to the third man boundary for a 36th four.
It was a rare false stroke in a chanceless innings and, when Gale called a halt after Adil Rashid edged Mark Footitt to the wicketkeeper, Lees returned to the pavilion with the joint-11th highest score by a Yorkshire batsman against his name, having faced 436 balls and hit 38 fours and a six.
Derbyshire had to score 468 to save the follow-on but lost Chesney Hughes, who scored 270 not out against Yorkshire earlier this season, to Ryan Sidebottom in the seventh over for 12.
Wayne Madsen walked after inside-edging Patterson to the wicketkeeper in a set of six that also saw Wes Durston depart and Brooks struck twice in successive overs to leave Derbyshire with a lot of work to do to avoid another defeat.