Marcus Trescothick made the highest score in a 40-over match at Chester-le-Street, but Somerset had a late fright before edging a tense win.

Trescothick (124) dominated a 175-run partnership with Justin Langer as Somerset set a target of 286-8.

Durham struggled in response, with Charl Willoughby taking 4-30.

The home side were reduced to 187-9 before some late heroics from Liam Plunkett (72) and Steve Harmison (25 not out) came up 18 runs short.

The pair put on 81 runs for a new record 10th wicket stand for Durham.

Plunkett produced a magnificent innings of 72 off 43 balls, combining some big hitting and a cool head before he was unfortunate to be run out by Alfonso Thomas with Durham close to the finish line.

Prior to their late fireworks it was an unusually poor performance from in-form Durham.

They had no answer to the Trescothick onslaught as he scored his 124 off 97 balls to beat the 115 made by Phil Simmons for Leicestershire at the same ground in 1996.

Trescothick reached his hundred off 73 balls and his partnership with Langer lasted 24 overs before the Australian holed out at deep mid-wicket off the bowling of Paul Collingwood after making 63 off 65 balls.

England all-rounder Collingwood was the only Durham bowler to have any joy, finishing with 3-52.

Somerset's innings stuttered somewhat when Trescothick was run out by a direct hit from Shivnarine Chanderpaul after a mix-up with Omari Banks.

When Banks then ran himself out in the next over, it caused Somerset to stumble when they should have scored over 300.

But Willoughby struck early to remove Di Venuto and when Collingwood holed out to Zander de Bruyn off Willoughby and Chanderpaul played on to his own stumps facing his first ball, Durham's task looked a tough one.

Mark Turner then removed Phil Mustard and Will Smith while Ben Harmison was caught behind off Willoughby.

It left Durham on 66-6 and in danger of an embarrassing defeat before Dale Benkenstein steadied the ship in a partnership of 87 with Gareth Breese.

They departed in quick succession and Graham Onions could only add five to leave Durham requiring 100 from their last wicket pairing.

It looked an impossible task before Plunkett and Harmison's late flurry.