ALASTAIR Cook may not play very much for Essex again this season, but England's Ashes opener signed off from county duty in spectacular style with a brilliant Twenty20 Cup hundred against shell-shocked Surrey at The Oval.

Cook and Mark Pettini added 169 for the first wicket in Essex's total of 210 for three, and Surrey slid sadly to 126 all out in reply.

Essex remain on course for a quarter-final place but Surrey's dreams of reaching the knock-out stage are in tatters after defeats on successive evenings.

England rarely play Cook in limited-overs cricket - he has been back at Essex for the past six weeks following the May Tests against the West Indies and was not chosen for the World Twenty20 - but his 100 not out in a South Division game watched by 17,000 spectators basking in the early evening sun came off just 57 balls, and included 11 fours and four sixes.

The 24-year old left-hander, who joins up again with England's Test squad this weekend, warmed up by hitting the first three balls of the second over, from Chris Jordan, all for four.

His first six was struck straight off Grant Elliott, taking him to 47, and after reaching his half-century from 34 balls he pressed the accelerator down still further.

Two more sixes were swung from successive balls into the Bedser Stand off Matt Spreigel's off spin, and his final six was driven high over long on at the start of the 20th over, from leg-spinner Chris Schofield, which cost 22.

Cook then reverse swept the next ball for four, to go to 97, and a scampered two to long off and a single into the legside took him to his century.

Just for good measure, Ryan ten Doeschate then thumped the final ball of the innings for yet another six - the 10th in Essex's huge total of 210 for three - to complete Surrey's misery.

Pettini, the Essex captain, was also in superb form, hitting 87 from 53 balls, with four sixes and 10 fours.

Pettini and Cook's opening partnership of 169 is the second highest first wicket stand in Twenty20 history, behind only the 175 put together by Graeme Hick and Vikram Solanki for Worcestershire against Northamptonshire at Kidderminster two years ago.

Surrey lost the wickets of Scott Newman and James Benning in Graham Napier's two new ball overs, and only Mark Ramprakash, with 26, and Usman Afzaal, who hit 30 off 16 balls, even hinted at being capable of launching a meaningful challenge to the daunting Essex score.

Pettini, who also scored an unbeaten 80 from 57 balls in Essex's last Twenty20 match, a victory against Middlesex, has dramatically shaken off early-season struggles with the bat in the past fortnight, and is now cashing in with runs in both Championship and one-day cricket, but it is Cook's form which will be most eye-catching to the wider world.

Before this season he had hardly hit a six in his whole cricketing life, but eight Twenty20 Cup matches this summer with Essex have clearly broadened his approach.

In this Twenty20 Cup he now has 337 runs at an average of 48.14, and an impressive strike rate of 144 runs per 100 balls.

His four sixes doubled his six-hit tally in the competition, while there have been 36 fours besides.