Sam Cook took nine wickets as Essex and Northamptonshire shared 25 wickets on a bonkers first day on their LV=Insurance County Championship clash.

Northamptonshire were skittled for 81 – with Cook grabbing five for 21 and his 50th scalp of the season – before Essex were restricted to 170 and an 89-run first-innings lead.

The visitors then lost five wickets against the new ball to end the day 23 for five, a deficit of 66, with Essex knowing a victory will hand them the Division Two trophy.

Cook ended with incredible day figures of nine for 29, already a career-best.

Having won the toss and batted, Ricardo Vasconcelos was the first of seven leg before victims – a joint record for Essex – before Porter pinned him in the third over.

Luke Procter saw his off stump cartwheeling backwards, Rob Keogh was lbw to Cook and Saif Zaib plumb in front to Shane Snater – the visitors 36 for four.

Gay showed skill in his innings – mixing five boundaries with vague stickability – although was slow to get his bat down to be lbw to Porter.

Josh Cobb, on his first red-ball appearance in two years, handed Cook his 50th scalp of the season when he was lbw before Tom Taylor edged behind three balls later.

Adam Rossington swept a six but was lbw next ball, Simon Kerrigan was lbw to give Cook his fifth and then Porter rounded off the innings by producing an edge off James Sales’ bat, which flew to Alastair Cook at first slip.

During the lunch interval, Essex bid farewell to club legend Ryan ten Doeschate and retired the No.27 shirt – the Holland international returning after 19 seasons at the county.

Despite it being high-quality bowling rather than gremlins in the pitch that cost Northamptonshire, Essex attacked in reply.

They had wiped out Northamptonshire’s total by the end of the 15th over, however had lost their first four wickets by the same point.

Nick Browne lasted until the sixth over when he edged to first slip, Essex having already scored 39, before Alastair Cook pushed to third slip.

Josh Rymell was bowled through the gate by Procter and Lawrence – standing in as captain with Tom Westley’s wife expecting the couple’s first child – was caught by Berg after a 999mph innings fully of wristy shot play.

Michael Pepper and Simon Harmer both tamely edged to point, Paul Walter played over a straight ball to be bowled by Taylor, Snater and Sam Cook tickled behind and Wheater rounded off the innings when he was bowled for 34.

Essex won a first-innings lead and in 13 evening overs managed to make inroads as Vasconcelos was lbw to Cook and Gay flicked Porter behind.

Keogh was caught Cook bowled Cook, nightwatchman Kerrigan nicked off and second nightwatchman Sales was castled to the last ball of an exhilarating day.

Essex fast bowler Sam Cook, who took nine wickets in the day: “We rocked up loss the toss but we like to bowl first here at Chelmsford especially with the 10:30am start. It started like a pretty decent wicket which didn’t have a heap of movement.

“Ports started really well and it was nice to back him up and then the rest of the day was a bit of a whirlwind.

“On a personal level I liked the pitch but I think when the ball does a bit both teams played pretty positively and there were shots from both teams in there they probably won’t be too happy with.

“When you get on a roll on these sorts of days you have to keep your rhythm and keep on putting the ball in a good area – and we managed to do that.

“There is a bit there but I don’t think it is drastic, there is just enough. Sometimes when it is the odd ball it draws you in as a batsman. Sometimes it is the pitch which doesn’t do it every ball that gets you wickets as a bowler – I think that is the case today. Some days all the nicks carry and all the lbws are given.”