Glamorgan 252 (Wallace 61, Wagg 57) and 50 for 1 lead Sussex 283 (Nash 132) by 19 runs
Graham Wagg's burst of three wickets in four balls completely changed the course of Sussex's innings and also the game as the visitors lost their last eight wickets for only 51 runs in 25 overs. The Glamorgan seamer thrived in the cloudy conditions, and during his spell also claimed his 200th first class wicket for Glamorgan.
Sussex were indebted to Chris Nash, who struck the 22nd century of his career, before Glamorgan reached 50 for 1 in their second innings, a lead of 19.
Sussex had resumed on 111 for 1 with night watchman Danny Briggs giving Nash useful support, and the second wicket pair had added 69 before Nash called his partner for a risky single in the last over before lunch with Briggs comfortably run out for 36.
Briggs had been fortunate to survive an excellent opening spell against Timm Van Der Gugten who regularly passed the outside edge, but Briggs' determination carried him through until his dismissal.
Nash, meanwhile played watchfully, sharing a partnership of 52 with Luke Wells before Wells was bowled by Craig Meschede, and at 232 for 3, Sussex were in sight of a substantial first innings lead before Wagg's dramatic over and the subsequent collapse.
Nash had completed his third championship century of the season from 284 balls with eighteen fours, when Wagg began his eighteenth over; with his second ball Christian Davies edged to the wicketkeeper, his fourth dismissed Luke Wright who wafted outside the off stump, then the next delivery bowled David Wiese.
An early tea was then taken because of bad light, which might have made the three batsmen dismissed by Wagg wonder why the decision had not been taken before the over had started.
After the break, Nash's six and half hour vigil ended when he was bowled by Van Der Gugten for 132, and the tail quickly followed with Glamorgan's seamers rewarded for their accuracy throughout the innings. Apart from David Lloyd, who only bowled one over, Van der Gugten, Meschede and Wagg's economy rate was under three runs an over with Hogan's under two.
When Glamorgan started their second innings, 31 runs adrift, Selman did manage to get off the mark after four successive ducks, but did not last long before he was leg before in Steve Magoffin's second over.
Glamorgan vs Sussex
Specsavers County Championship Division Two
England Domestic Season