Joyce's masterful double hurts Derbyshire
Sussex 468 for 5 (Joyce 250, Wells 116) lead Derbyshire 191 by 277 runs
Joyce, the former Sussex captain, scored 250 from 327 balls, the highest of his first-class career, while Wells made 116 and shared a second-wicket stand of 310 in 85 overs.
It was the highest for any wicket by Sussex against Derbyshire with Joyce plundering 34 fours and two sixes before he was lbw to the offspin of Wes Durston who also dismissed Wells but the visitors ended day two on 468 for 5, a lead of 277.
Derbyshire knew they had to strike early to get back in the game and the chance came and went in the seventh over of the morning when Joyce was put down in the covers.
He was on 47 out of 103 when he mistimed a drive at Andy Carter but Hamish Rutherford spilled a low chance and Joyce made them pay a high price as he and Wells batted through the first two sessions.
At least Derbyshire made them work harder for their runs before lunch when they scored only 70 in 32 overs but the pitch had eased considerably and the watchful accumulation in the morning allowed the pair to step on the gas in the afternoon.
Billy Godleman used six bowlers before lunch and even turned to the occasional spin of former captain Wayne Madsen but, the occasional false shot apart, there was little to encourage the home side after that early miss.
The tone for the rest of the day was set shortly after lunch when a top-edged pull by Joyce off Carter cleared the ropes and he reached his century when he nudged his 180th ball into the covers for a single.
Derbyshire claimed the new ball immediately but it made little impression as Joyce pulled and cut Luke Fletcher for boundaries before Wells whipped Andy Carter through midwicket to bring up the 200 stand.
There was no sign of nerves as Wells moved quickly through the nineties with two fours from Shiv Thakor and reached his century shortly before the end of the second session which had seen Sussex double their morning's output.
What came after tea was carnage as Joyce smashed Fletcher out of the attack with five consecutive fours before taking another four boundaries from a Carter over.
He survived another dropped catch on 170 when Durston could not cling onto a sharp chance at second slip and after pulling Carter for two more fours, raised his bat to acknowledge a superb double century which had come from 286 balls.
His fourth fifty came off only 26 balls and although Derbyshire finally broke through when Wells drove at Durston and was smartly taken by Madsen at slip, Joyce passed his previous best first-class score of 231 and scored 107 in gthe evening session before Durston trapped him lbw.
Thakor removed Ross Taylor and Matt Machan chaeply but unless rain intervenes, it is hard to see Derbyshire denying Sussex victory.