Surrey 313 for 8 (Davies 82, Roy 55, Burns 52) beat Essex 247 (Ryder 131, Dernbach 4-41) by 66 runs
Jesse Ryder slammed 131 off 110 balls, but could not prevent Essex falling to their first Royal London Cup defeat of the season.
Essex paid the price for losing half the side for 119, chasing Surrey's 313 for 8, though while Ryder was at the crease anything looked possible, particularly when he was putting on 91 in 11 overs with Ashar Zaidi for the sixth wicket. Once both went in the space of three balls to Jade Dernbach, Essex resumed their earlier dismal form and finished 66 runs short.
Dernbach returned figures of 4 for 41 as Surrey, finalists last season, won for only the second time in this year's 50-over competition. His colleagues had been thrashed around Chelmsford by Ryder, who struck four sixes and 13 fours in his innings, accelerating from fifty to his hundred in 33 balls.
The base for Surrey's large total was laid by Steven Davies, who hit 82 from 81 balls and was ably supported by fifties from Jason Roy and Rory Burns, as well as 41 from Aaron Finch and 45 from Ben Foakes, after they had elected to bat.
Finch put on 94 for the first wicket with Roy before he was beaten by one that kept low from David Masters. Masters, Graham Napier and Zaidi kept the shackles on the openers until Matt Quinn returned for the 13th over and Roy hit him 6, 4, 6 from successive balls to put the Surrey innings into full swing.
Roy reached his half-century off 52 balls with a reverse-swept four off Dan Lawrence. But eight balls later the England batsman fell victim to an incredible sleight of hand by James Foster, who whipped off the bails when Roy reached for a ball down leg side from Lawrence.
Davies and Dom Sibley posted fifty for the third wicket in nine overs before Sibley drove Bopara to midwicket where Zaidi held on to the catch. Davies then moved to his personal fifty, from 52 balls and with only three boundaries.
He found another willing partner in Burns and together they put on 92 in 14 overs. Davies departed for 82 when he moved well outside off stump to try and deflect Ryan ten Doeschate towards third man and was caught by Foster. Burns pulled Napier for his seventh four to bring up his half-century in 47 balls, but next ball tried something similar and was caught on the midwicket boundary by Nick Browne.
Matt Pillans lofted one down Bopara's throat at long leg to give ten Doeschate a second wicket, and then Gareth Batty followed suit - ten Doeschate taking the catch on the same spot and Bopara claiming his second wicket.
Surrey were helped past the 300 mark when Quinn was hit for a third six to long off by Foakes as he condeded 56 from his six-over spell. Bopara restricted himself to just five overs but took a third wicket when his last ball found Foakes looking to heave the six that would have brought up his fifty, and missing the ball completely.
Mark Footitt broke the Essex opening partnership when he had Tom Westley caught in the covers by Stuart Meaker, and then Browne swished outside off stump at Dernbach to give a catch behind. Bopara went to an outstanding catch by Davies, diving low down to his right at first slip, and Lawrence wafted at Meaker to give Foakes a catch down the leg side.
Ryder lofted Batty over deep mid-off for his sixth four to bring up Essex's hundred and his own fifty, which took 53 balls, and then drove the same bowler high over long-off for six. But after a 50-run partnership for the fifth wicket, Essex lost ten Doeschate lbw to Pillans.
Zaidi cleared the sightscreen at the Hayes Close End for six off Batty but played second fiddle to Ryder. The Kiwi added two more maximums off Pillans, one straight, the other over midwicket. He went to 99 with his final six, pulled over midwicket off Meaker, and then chopped the single that took him to his century from 86 balls.
The returning Dernbach broke the rampant partnership when he had Zaidi caught down low by Foakes, and then Ryder taken on the midwicket boundary. Foster went lbw to Sibley, Napier provided a fourth catch behind for Foakes and Masters gave Batty a wicket to end the game nearly nine overs early.