Alastair Cook scored his first Specsavers County Championship century since 2014 and shared in a record-breaking stand with Tom Westley before Gloucestershire hit back in their Division Two match at the Essex County Ground.
Cook made 105 and Westley 121 before rain brought an end to the day’s play 19 overs prematurely with Essex 287 for six in response to their opponents’ 262.
The pair put on 222, an Essex record for the second wicket against Gloucestershire, beating the 192 involving Paul Prichard and Jon Lewis in 1994, also at Chelmsford.
But once their partnership was broken, wickets fell steadily as the bowlers, with the help of the new ball, started to find movement under gathering clouds that saw the introduction of the floodlights.
While the sun shone, Cook and Westley warmed to their task with considerable ease and effect, adding 125 before lunch after resuming on 39 for one. Both pulled and drove with authority as they completed their individual centuries.
Westley was the first into three figures, the milestone arriving from 198 balls and containing 18 fours, while Cook reached his ton from 182 deliveries, 16 of which he despatched to the boundary.
Both were eventually dismissed by Jack Taylor. The off-spinner had only bowled one over before lunch but with his first ball of a new spell after the interval, he trapped the England Test captain leg-before wicket.
Then in his fifth over, he had Westley caught by Gloucestershire skipper and wicketkeeper Gareth Roderick with a delivery that climbed on him.
The new ball was taken with the score on 249 for three, and brought Gloucestershire quick successes.
Fast bowler Liam Norwell beat the defence of Ravi Bopara after he had made 14 with a ball that cut back before Josh Shaw produced a similar delivery that accounted for Ryan ten Doeschate, the Essex captain offering no stroke and perishing leg-before wicket.
Just before that, young paceman Shaw picked up his first wicket on Championship debut when Dan Lawrence top-edged a pull to Hamish Marshall at mid-off.
Those three wickets fell in the space of 18 deliveries for just 10 runs but rain was to arrive before the visitors had the chance to inflict further damage.
Norwell, the pick of the bowlers, has so far picked up 2-64 in 25 overs while Shaw, on loan from Yorkshire, and Taylor have also bagged a couple each, the latter claiming his two wickets at a cost of only 12 runs in nine overs.