Brydon Carse keeps Durham's victory push on track as Essex show the fight of champions

Nobody expected the champions to roll over without a fight. And sure enough, after an indomitable lower-order display featuring three career-best performances, and a raucous burst with the new ball in which Durham came within a fingertip of being three-down with no runs on the board, Essex were still brawling as the shadows lengthened at Chelmsford. They've carried this fight into the fourth and final day of a contest that, at one stage, seemed unlikely to extend beyond two.

But, with Brydon Carse rising above another unresponsive Chelmsford deck with a back-bending (and ankle-buckling) five-wicket haul, Durham had regained their nerve by the close, thanks to a pair of contrasting innings from Jack Burnham and Scott Borthwick, whose over-my-dead-body display eked out nine unbeaten runs from 88 balls - a stark contrast to his thrilling first-day hundred. His team will need 108 more runs with seven wickets standing when play resumes, and with the ever-menacing Simon Harmer yet to have his say, anything less than drama would be an anti-climax.

With a lead of 45 overnight, and four wickets still in hand, the smart money might have been on Harmer himself, 6 not out at the start of play, to seize the scenario, and coax a lead that he would back himself to defend in the fourth innings. So when he shuffled across the crease to Ben Raine's third ball of the morning to be pinned lbw without adding to his score, Durham celebrations were unfettered. It felt like a decisive step towards victory.

But as Essex and Worcestershire discovered to their mutual cost last week, a well-organised tailender with a solid defence has little to fear at Chelmsford this season. With Paul Walter setting the example for the lower-order with a series of lanky strides onto the front foot, en route to his own career-best of 77, Ben Allison emerged at No. 9 to produce an extraordinarily disciplined knock - 52 from 163 balls all told, with scarcely a sniff of a chance.

It was his maiden first-class fifty, and as Matt Salisbury had shown in similar circumstances on the second morning, his obduracy ensured that Durham were distracted by the mounting lead even as they tried to focus on the breakthrough that would bring the end of their toil that much closer.

Allison's most forceful stroke was a crunching drive as Chris Rushworth overpitched with a second new ball that offered less than Durham had anticipated, and he also benefited from four overthrows as a wild shy disappeared through cover. For the most part he dealt in arrow-straight pushes, finding the gaps rather than seeking them, as Essex's eighth and ninth wickets both contributed priceless fifty stands to the cause.

Walter, almost in solidarity, barely veered from the appointed method either. His first scoring of the morning was a scything cut through point to reach his fifty from 74 balls, but beyond that he needed nothing more than a big stride and a broad bat to blunt Durham's intentions. Their stand had extended to 58 in 23 fruitless overs when Carse was recalled for his second spell of the morning. His first ball to Walter was right in the corridor, angling across the left-hander, and grazing the edge with just a hint of extra bounce. It was a priceless incision that his team-mates hadn't looked like forcing.

Allison and Sam Cook negotiated the rest of his spell - not without a few alarms - but Essex's determination was not to be undone. More of the same was all that the dressing room ordered after the pair had reached lunch with a lead of 114 in the bank, and it duly arrived, with Allison reaching his fifty from 144 balls with a chop through point off Borthwick, and Cook rising to a familiar theme with nothing more ambitious than a series of deflections to visibly deflate the visiting attack.

Arguably it was only the taking of an early tea at 2.50pm, ahead of an 80-minute interval for the Duke of Edinburgh's funeral, that prevented even greater riches for Essex's tail. Upon the resumption, Allison lasted just three more balls, as that man Carse capitalised on the break in his concentration to thump his pads before his feet could get moving again.

Two overs later, Carse had ended Cook's resistance too, though not before a scare as he went over his ankle in his followthrough and needed lengthy on-field treatment. But Essex had done the needful. A lead of 168 was very much in the ball-park they had been eyeing up after shipping a near-identical first-innings deficit, and the manner in which they set about defending it was awesome to behold.

As Sam Cook showed with a similarly thrilling burst against Worcestershire last week, this Chelmsford wicket is currently all about the new ball, and he didn't waste a drop of it as Durham were rattled to their core from the outset. His very first ball, to Will Young, jagged in on the angle just enough to thump the outside of his off stump as he raised his bat for a leave, and at 0 for 1, it was a different game already.

One over later, Jamie Porter joined the fun. He'd been denied a first-over lbw by the width of a seam after being deemed to have pitched outside leg to Alex Lees, but now a near-identical delivery got the verdict to trigger ecstasy among his team-mates. That turned to agony two balls later, as David Bedingham fenced to slip and the ball died on Alastair Cook as he stooped forward to gather, but the tone of the innings had been set.

It wasn't until the 35th ball that Durham opened their account with Borthwick's tickle into space on the leg-side, by which stage the skipper was so deeply entrenched in his safety-first mindset that nothing and no-one was about to shift him up a gear. It was Bedingham who made the first tentative strides towards proactivity, with a brace of deflected fours through third man to get his innings underway, before Durham's first real shot in anger, a firm on-drive for four off Porter.

But Essex weren't done yet. Harmer had entered the attack in the ninth over, with Durham still stuck on a sickly 6 for 2 - now Cook changed ends to keep the hammer down, and quickly ended Bedingham's progress via a flimsy cut to point, a soft dismissal in the hardest of circumstances.

Burnham, however, had seen enough to know that Borthwick needed someone to stay busy while he focused on endurance, and in the closing half-hour of the day, he just began to give the sense that he had got the measure of the chase. With bold use of the feet to Harmer, in attack and defence alike, he chipped a cathartic four up and over mid-on before nailing a brace of fierce sweeps to prevent Essex's senior spinner from settling into a rhythm, despite a permanent encampment of four close catchers. And when Lawrence entered the attack for a sighter late in the day, Burnham had sufficient confidence to launch a half-tracker out of the ground at square leg. Similar bottle will be required to see this contest through. Three-year winning streaks don't get undone without an almighty struggle.