Essex's Fortress under siege as Durham close in on famous Chelmsford victory

After 12 matches and almost three years, the Fortress is on the brink of being conquered. Two half-formed comebacks in consecutive days, this time with their newest golden boy Dan Lawrence to the fore, cannot distract from the sort of frailties that have not been seen in Essex's cricket for several seasons - ones that have left Durham on the brink of a seismic victory in the champions' backyard.

By the close of the second day, Essex had eked out a lead of 45 with four wickets still to come - and they will be able to look to Durham's own close-of-play position on day one to know that, on this misleadingly placid deck, there could and should be plenty of resistance still to come. But with Scott Borthwick capping a superb captain's performance with two late wickets, and the extra pace of Brydon Carse prising out the two vital wickets of Lawrence and Tom Westley, Durham showed the same hunger in the field that their lower-order had displayed with the bat. It'll take something truly remarkable for this position to now slip from their fingers.

The early signs that Durham were not for buckling came as play resumed in the brightest, most summery conditions of the match. After picking up four wickets for as many runs in the previous evening's gloom to reduce their visitors to 148 for 8, Essex no doubt fancied their prospects of making hay in their second innings as soon as their opportunity came - whatever the deficit, they surely couldn't make as many errors as they produced on the first morning of the contest.

But they were never given a sniff of an early re-insertion, as Stuart Poynter and Matt Salisbury knuckled down for a ninth-wicket stand of 94 that grew in stature as the morning progressed. Essex opened with their likeliest partnership of Sam Cook and Simon Harmer, but they were each defied with ease, with Cook leaking a pair of soft-handed boundaries through third man that confirmed the pitch's lack of menace now that the clouds had rolled away.

And Essex's frustration grew as steadily as the confidence of the two batsmen, and the size of the lead. Salisbury defied a previous first-class best of 37 by climbing onto the front foot to club Harmer down the ground for four - a shot that was wildly acclaimed on the Durham balcony - before Poynter rocked back to greet Jamie Porter's first ball with a hard-handed crack through point. And even when Harmer exacted his revenge against Salisbury, inducing a lob to short leg for 42, Chris Rushworth strode out at No. 11 with every bit as much intent to loiter.

Lawrence by this stage was on to partner Harmer in a twin-spin attack, but Rushworth responded with a volley of three sublime boundaries - including an inside-out drive through the covers to take the lead past 150. Sam Cook had to be recalled to restore order, inducing a third-ball nick to slip that brought an early lunch, but with a lead of 163 secured, and Poynter unbeaten on 52, the session had delivered riches far beyond anything that Durham could have wished for.

The stage was set, therefore, for the champions to show their mettle, but sadly for Nick Browne, he never looked like being the man to deliver. He escaped his pair by the skin of his teeth, with an uncomfortable leading edge through the covers after edging short of slip, but two balls later, he climbed into a dreadful drive to an inducker from Rushworth, and lost his middle stump as he knelt through his stroke in resignation.

At the other end, there was Alastair Cook - and whoever dares to write off English cricket's most decorated nugget? But for the fourth innings in a row, he produced a curious blend of mindsets - with a brace of pinged cover-drives hinting at a fluency that he never quite showed in any other facet of his game. He'd ground along to 12 in the best part of an hour, before flicking uppishly to a leg-stump half-volley from Salisbury, and Jack Burnham at midwicket swallowed the offering with glee.

From 19 for 2, Essex needed their two in-form batsmen to show their mettle, and for the next 34 overs they did just that. Westley, a double-centurion in the season opener against Worcestershire, was joined by Lawrence - whose first-innings 32 had been bettered only by the rampant Borthwick on that manic first day. And between them they chipped away at Durham's lead in a stand of 103 that ought to have given their side the platform for a genuine fightback.

Arguably, Essex's first-innings agenda had been set by Westley's flighty drive, and he had to overcame a few more anxious moments early on, as Salisbury in particular challenged his outside edge. But Lawrence, at the start of a summer in which most of his fellow Test batsmen are either injured, or at the IPL, or out of form, or all three, slipped effortlessly into the higher gear that showed he's not about to shy away from the hard yakka now that he's broken into the England set-up.

After getting off the mark with a deflection through third man, he found the extra pace of Carse particularly to his liking as he rifled a pair of cuts through backward square, before showing off his wristy timing with a sublime pick-up off the toes from Ben Raine. And as he crashed Salisbury through the covers to bring up his first half-century of the season, the confidence being projected by Lawrence was palpable. So long as was on hand to set the terms for Durham's fourth-innings target, there was no reason for Essex to believe that the game was out of reach.

But then came the fatal lapses that have undermined Essex's performances all match long. On 38, Westley lost his shape as Carse induced a gruesome back-foot waft to first slip, and though Lawrence kept cracking on in the same forthright manner, Carse would have his number too four overs later. Another back-of-a-length delivery lured a flat, hard pull through midwicket - but Lawrence connected almost too well with the stroke. It fizzed to Will Young at deep midwicket, who made a crucial chance look simple.

Now Essex were truly rudderless, as Paul Walter and Ryan ten Doeschate clawed their way towards a lead with a series of imposing, but rattled boundaries. On 16, ten Doeschate attempted to biff a half-volley from Borthwick back down the ground, but managed only to scuff it in the air for the bowler to cling onto a blinder, diving across the crease. And the captain put his personal seal on the day two overs later, as Adam Wheater was done in by a ripping legbreak outside off, edging through to Poynter for 6.

At least Walter was still there at the close, one away from a gutsy half-century, and Harmer's presence for day three will be a very visceral reminder of what could yet happen if Essex are allowed to build a defendable lead. You can be sure that he'll defend every run with personal gusto. But the drawbridge has been lowered and hordes from the North are closing in. You can't imagine many prisoners will be taken in the final reckoning.