Essex 31 for 1 trail Warwickshire 517 (Lamb 173, Hain 82, Patel 51*) by 486 runs

Essex have not conceded so many runs since Hampshire piled up 525 for 8 in the first innings at Southampton in the opening match of the season, when they lost by an innings and 87 runs. Having gone unbeaten since, chalking up eight victories and eyeing up a second County Championship in three years, this would not be a timely moment to become reacquainted with defeat.

Such an eventuality is some way off. Unless Jeetan Patel can coax a greater response from a slow pitch than Simon Harmer achieved in 60 overs of trying, the likeliest result is a draw. Nonetheless, with leaders Somerset building a considerable advantage against Yorkshire at Taunton, this could be a critical moment in the race for the title.

For Warwickshire's part, a draw and a handful of bonus points would do very nicely, almost certainly banishing any lingering anxiety about relegation with Nottinghamshire heading for yet another defeat.

At the heart of Warwickshire's rare prosperity was a magnificent innings from 23-year-old Matthew Lamb, who turned his maiden first-class century into a seven-hour marathon that eventually saw him out for 173, which is, after Dom Sibley's double-hundred at Canterbury in June, the highest score by a Warwickshire batsman this year.

Lamb's potential has long been waiting to blossom. Warwickshire identified his talent when he was only 11 and he made his Birmingham League debut at 13. His first-class debut for the county came in 2016 but although he made a couple of half-centuries the following year he has not been able yet to nail down a place. Although he made a good impression in T20, his first six first-class innings this year yielded just 29 runs in total and he would not be involved in this match but for four batsmen being injured.

There is a fair chance he will be picked for the next one, having batted with a solid technique and considerable maturity in the face of an Essex attack not helped much by a slow pitch but who nonetheless offer one of the bigger tests he will have faced thus far. Jamie Porter and Sam Cook had bowled well without much luck on the opening day and Simon Harmer, as he has demonstrated time after time in taking 200-plus wickets in three seasons with Essex, tests a batsman's skill in any conditions.

Lamb had some moments of fortune, although not before he had recovered from the setback of losing Sam Hain's company in the seventh over of the day and held his nerve to complete a 211-ball hundred with his 15th boundary. He was caught at slip off a Ravi Bopara no-ball on 104, survived a huge appeal for caught behind off Porter on 106 and was dropped on 110 in an incident that also saw Essex appeal for a run-out, which was upheld and then rescinded.

Alastair Cook, moving to his left at first slip, spilled the chance when Porter found the edge. Harmer, standing next to him at second slip, retrieved the ball and threw down the stumps. Lamb was well out of his ground but, after the umpires conferred, was invited to continue his innings, the apparent conclusion being that he had deserted his crease only under the misapprehension that he was out caught, in which circumstances under a recent tweak to the Laws, a batsman can be deemed to be not out.

Harmer said later that he had been happy to withdraw the appeal and Lamb confirmed that the Essex fielders had made it clear to him that, as far they were concerned, he should not be out.

How he made the most of that let-off, adding a further 10 boundaries and, having helped Hain add 150 in 49 overs for the fourth wicket, enjoying the benefit of another resilient partner in Henry Brookes, with whom he shared a 105-run partnership for the seventh wicket that was the key passage of the day in securing such a strong position for their side.

Immediately before they came together, three wickets had fallen for seven runs in the space of 22 balls. Michael Burgess had followed Hain in edging into the slip cordon, Harmer grabbing a superb catch low to his left at second slip, before the debutant Ethan Brookes - Henry's younger brother - popped a ball from Harmer into the hands of leg slip.

Brookes the elder proved to be the perfect partner, although Lamb ultimately repaid him by calling for a risky single to leg and running him out four runs short of what would have been his fourth career half-century. "I owe him an apology for that," Lamb said after Harmer had gathered and scored a direct hit with his throw. "It was my fault completely."

Patel further turned the screw with a half-century of his own before Harmer, who had only once bowled 50 overs in an innings for Essex and never 60, dismissed Olly Hannon-Dalby and George Garrett to finish with 6 for 143.

"It was a pretty frustrating day for us," Harmer said. "There is not much in the pitch. If we can bat well then you would expect the match to end in a draw but you never know what could happen when we get to day four."

The Essex reply, though, did not get the start they wanted in the 15 overs they had to negotiate before the close, Patel striking an early blow when Cook edged him to second slip.