Gloucestershire 255 for 9 (Charlesworth 71, Harris 52, Patel 5-93, Potts 2-35) trail Durham 445 (Clark 100, de Leede 65, Coughlin 59*, Borthwick 53) by 190 runs
Durham spinner Ajaz Patel put the skids under Gloucestershire on day two of an increasingly one-sided LV=County Championship encounter at Bristol's Seat Unique Stadium.
The slow left-armer claimed a season's best haul of 5 for 93 and England paceman Matthew Potts weighed in with 2 for 35 as Gloucestershire were reduced to 255 for 9 in reply to Durham's imposing first-innings 445.
Marcus Harris and Ben Charlesworth offered defiance aplenty in contributing battling half-centuries as the hosts advanced to 139 for 2, only to then suffer an alarming collapse in the final session, losing seven wickets for 88 runs.
Wheeling away from the Bristol Pavilion End, Patel ripped through the tail, claiming three of his five victims in an early-evening burst which left him on a hat-trick. Gloucestershire managed to register a batting bonus point before the close, but still trail the Second Division leaders by 190 runs and require a further 41 runs to avoid the possibility of being made to follow-on.
His prospects of featuring for England in the upcoming Ashes series improved by injuries to Jofra Archer and James Anderson, Durham spearhead Potts was out to impress and add to the 23 victims accrued in four previous matches this season. He began well enough, removing Chris Dent lbw with a ball that came back into the left-hander and was destined to hit the top of middle and leg with the score on 10.
Bowling with more pace and accuracy than any of Gloucestershire's bowlers had managed on the first day, Potts created no end of problems for the home side's second-wicket pair, going past the bat with sufficient regularity that, on another day, might easily have yielded four or five wickets.
His battle with Australian opener Harris served as a potential precursor to future contests, while Charlsworth lived a charmed existence at times as he played and missed in the face of 11 overs of sustained hostility spread across two spells either side of lunch.
For his part, Harris had good reason to wish to sign off with an innings of substance on his last appearance before joining the Australian squad ahead of the ICC World Test Championship final against India at The Oval, beginning on June 7. Yet he could easily have gone in the first over without scoring, slapping a shortish delivery from Ben Raine straight to point where Bas De Leede was unable to hold on.
Harris made good his escape to contribute a carefully crafted half-century, his first since early April, affording Gloucestershire's reply the reassurance of solid foundations. His ninth boundary, steered behind point, served to bring up his 50 and raise the hundred partnership for the second wicket.
Unfortunately for his Ashes ambitions, Harris was out next ball for 52, caught behind off a quicker delivery from Patel. The product of sound technique, his innings spanned 120 balls. Whether it will prove sufficient to dislodge either David Warner or Matt Renshaw from the Australian top-order next month remains to be seen.
Given that batting became markedly more hazardous after an early afternoon downpour caused 13 overs to be lost, Charlesworth's diligence and powers of concentration were to be admired as he single-handedly attempted to haul his side to respectability.
Having survived the fire and brimstone generated by Potts, the left-hander demonstrated sound judgement in dealing with Patel, who now represented the chief threat to Gloucestershire. Certainly his temperament under duress suggests he is the man most likely to replace Harris at the top of the order when Championship action resumes next month.
Miles Hammond and Jack Taylor came and went disappointingly quickly from a Gloucestershire perspective, the former losing his off stump to Raine without offering a shot and departing for 21 and the latter bowled between bat and pad by Patel after striking two fours and a six in a brief innings of 16.
Relegated one place down the order owing to the joint burdens of captaincy and wicketkeeping, James Bracey departed with undue haste, making 14 before playing across the line to a Potts in-swinger and offering a catch to second slip as the hosts subsided from 139 for 2 to 189 for 5 either side of tea.
Unperturbed, Charlesworth continued to go methodically about his business, raising his second fifty in as many innings from 134 balls.
Although he was prepared to flirt with danger outside off stump, Zafar Gohar was at least able to provide more dependable support in a seventh-wicket alliance that, given the length of the tail, appeared pivotal to Gloucestershire's prospects.
But with the end of the day in sight, fatigue at last played a hand in proceedings, Charlesworth aiming a tired waft at a short-pitched ball from de Leede and offering a straightforward catch to second slip as the hosts lurched to 216 for 6.
An already parlous situation then became much worse, Matt Taylor driving loosely to mid-on without scoring, Zafar reaching forward and being stumped by Ollie Robinson for 18 and Zaman Akhter nicking to second slip for a duck as Patel claimed three wickets in five deliveries to cut through the lower order and leave the home side teetering on 227 for 9.
Only tail-end defiance from Josh Shaw and Ajeet Singh Dale enabled Gloucestershire to salvage a batting bonus point, a landmark that was greeted by ironic applause from a disgruntled audience.
Durham had earlier concluded their first innings with a flourish. Resuming on 393 for 9, the last pair of Patel and Paul Coughlin added a further 52 in 8.2 overs, serving as an irritant to opponents who were in a hurry to commence their reply.
Durham's first task was to accrue a fourth batting bonus point and Coughlin obliged, pulling Zafar over midwicket for a maximum to move Durham beyond 400. Looking extremely comfortable in benign conditions, Coughlin quickly moved to his 50, a landmark which occupied 43 balls and included seven fours and a brace of sixes.
Having not looked like taking a wicket in the previous 35 minutes, Gloucestershire no doubt breathed a sigh of relief when Matt Taylor found Patel's outside edge and Bracey wrapped up proceedings with the visitors still five runs short of a fifth bonus point. Coughlin finished unbeaten on 59 from 52 balls, while Patel, who made 22, played his part in a valuable last-wicket stand of 71.
