On a surreal day of 15 wickets on a capricious Chelmsford wicket, Somerset had red-ball wannabee Will Smeed racing across the breadth of the country from Wales to take up injury substitute duties in the Rothesay County Championship.

Smeed, 24 and yet to make his first-class debut despite plentiful experience in white-ball cricket, had just posted an unbeaten 209 for Somerset seconds against Cardiff students at Abergavenny when he got the call that he was required to come over and replace Tom Kohler-Cadmore, who had damaged his hand taking a catch.

At one point it looked to be touch and go whether Smeed, who wants to expand his career into the longer format, would make it in time to bat in the first innings as Essex threatened to run through Somerset, just as Somerset had done to the Essex batting earlier in the day.

Essex had collapsed from a comparatively healthy 77 for 2 nine balls before lunch to 149 all out by mid-afternoon, Josh Shaw wrapping up the innings with figures of 3 for 30 on his debut after moving from Gloucestershire. That Somerset did not fall apart after being 16 for 3, and had reached 179 for 5 at the close, was largely down to James Rew, who accumulated a patient 48, and some big-hitting by stand-in captain Craig Overton, who was unbeaten on 50 from 36 balls.

At the start of an eventful day in front of a bumper crowd of 3128, it had taken just eight overs for Overton’s decision to bowl first on a green-tinged wicket to bear fruit – and a further 43 overs to complete Essex’s downfall.

Jake Ball had looked lively from the start and made inroads with two wickets in three balls. Paul Walter had not looked particularly comfortable before falling lbw trying to whip a ball to leg that straightened. Wiaan Mulder’s first knock on home debut was over before it had begun as he received one that jumped up and took the edge to provide a catch so sharp high to Kohler-Cadmore’s right at first slip that it ended the fielder’s participation.

Dean Elgar and Charlie Allison brought a sense of relative calm to the Essex batting for 22 overs, while putting on 68 for the third wicket. But, as before, and again later, one wicket begat another.

Elgar fell into a carefully baited leg-side trap and chipped up tamely a Tom Lammonby delivery to the fine-leg boundary. Three balls later, Matt Critchley, the star turn last week in Essex’s innings victory at Hampshire with 173, tickled behind to depart without scoring.

Allison looked the most assured of the Essex batters, hitting six boundaries in his 49, until diverting a ball from Migael Pretorius low to first slip, a position now occupied by Tom Abell.

Michael Pepper hammered Shaw for two sumptuous cover-drives to the boundary but was bowled through the gate by Overton. The Somerset leader struck again two balls later when Simon Harmer was lbw to a ball of full length. And it got worse for Essex with a third wicket in 10 balls as Luc Benkenstein dragged on a wide ball from Shaw, who then accounted for Shane Snater and Jamie Porter.

Somerset sent in Jack Leach to open with Kohler-Cadmore now unavailable but the ploy failed as the erstwhile No. 11 was bowled 12th ball by a straight one from Porter. Lammonby went in short order, edging Essex captain Sam Cook low to first slip. And they were quickly three down when Josh Thomas nicked Cook.

Abell and Rew steadied things either side of tea, adding 57, before Abell nibbled at one from Snater. Rew was sensible in his resolve before Harmer turned one that took the left-hander’s outside edge. The first of two straight sixes by Overton off Harmer took Somerset into the lead.