Match scores (SWALEC Stadium)
Glamorgan won by 1 run
Glamorgan inns: 281-7 (50/50 overs. Ingram 142, Bragg 59, Carlson 36; Wagner 4-58, Ten Doeschate 1-30)
Essex inns: 280/9 (50/50 overs. Chopra 124, Bopara 56; de Lange 2-48, Hogan 2-42, Meschede 2-53)
Match report
Essex lost their 100 per cent record in the Royal London One-Day Cup as Glamorgan claimed a thrilling one-run win in Cardiff.
The hosts were indebted to Colin Ingram, who scored a superb 142 featuring eight sixes - two of which struck the pavilion roof.
Varun Chopra, who made 124, threatened to win the game for Essex but following his dismissal, panic set in and they were two runs short of the seven they required to win from the last over.
Glamorgan elected to bat but soon lost openers Jacques Rudolph and David Lloyd to New Zealand seamer Neil Wagner.
Ingram and Will Bragg then played with extreme caution against Wagner and James Porter and after the first 10-over power play the score had only progressed to 26 for two.
Their approach was rewarded, though, as the third-wicket pair put on 98 in 22 overs before Bragg, having scored 59 from 79 balls, was stumped down the leg side from Ashar Zaidi's left-arm spin - his second such dismissal in successive innings.
Kiran Carlson then joined Ingram and the 18-year-old, who top-scored in the previous game, again showed plenty of promise. With an array of attacking strokes, he scored 36 from 33 balls before giving Ravi Bopara a return catch.
Ingram reached his 16th one-day hundred and his third against Essex before launching a furious assault on the bowling attack - notably Ryan ten Doeschate, who was struck for three sixes in an over.
With 88 coming from the last 10 overs, Essex faced a challenging target of 282 and Glamorgan's opening attack struck immediately. Marchant De Lange had Nick Browne caught behind and Tom Westley was bowled by Michael Hogan to leave Essex two for two after nine balls.
The visitors then replicated Glamorgan's recovery as Alastair Cook and Chopra settled into a productive partnership. De Lange did not help Glamorgan's cause by greeting Chopra with three short-pitched deliveries that the batsman struck for sixes over the mid-wicket boundary.
Chopra reached 50 from 59 balls and the pair added 103 before Cook (37) gave a low catch to cover point.
Ravi Bopara then supported Chopra in a stand of 108, with Chopra reaching his third List A century for Essex and Bopara an attacking 56, before Bopara was unluckily run out when Craig Meschede dropped a return catch from Chopra only to deflect the ball on to the stumps at the bowler's end.
Essex then faltered, losing Adam Wheater and Chopra, who was bowled by Meschede, and at 239 for six, the visitors required 43 from the last six overs.
After Ashar Zaidi and Ten Doeschate were dismissed and Simon Harmer ran himself out, four runs were needed from the final ball with the last pair at the crease. Wagner could only manage two and Glamorgan won by the slenderest of margins.