Durham virtually guaranteed an unbeaten record for the season when Shivnarine Chanderpaul's first double century in the LV County Championship put Worcestershire under the cosh at New Road.

The West Indian left hander made an unbeaten 201 as the Division One champions ruthlessly reinforced their powerful overnight position by going beyond 600 for only the fourth time since becoming the 18th first-class county in 1992.

When Will Smith declared at 634 for eight - the fourth highest total ever made against Worcestershire - the relegated home side needed 278 to avoid closing their dismal season with an innings defeat.

Given 12 overs to bat before the close, they trimmed back the deficit to 237 but lost Stephen Moore leg before to Ian Blackwell in making 41 for one.

Chanderpaul extended the meaning of patience when facing 382 balls in an innings lasting nearly eight and a half hours.

His second hundred, compiled from 231 deliveries, occupied most of the third day and finally arrived when he unexpectedly unleashed a lofted boundary to long on.

In all he hit 25 fours - only nine of those in progressing from his overnight 100 not out - and initially there was some justification for his watchful approach.

Worcestershire's inexperienced attack benefited from more helpful conditions on a cloudy morning but, after dismissing Dale Benkenstein for 109, they were unable to ruffle, let alone break, Chanderpaul's concentration.

After completing his third hundred in four innings in the last over the previous evening, he was in a more obdurate mood, adding only 28 in 29 overs up to lunch in a clear indication Durham expected to bat Worcestershire out of the game.

When they resumed on 390 for three, Benkenstein needed nine more runs to post his fifth Championship century of the season. This arrived in the fifth over when he pulled Chris Whelan for his 18th four.

The partnership with Chanderpaul was worth 226 - only 24 short of Durham's record for the fourth wicket - when Gareth Andrew beat Benkenstein off the pitch for a catch by wicketkeeper Steve Davies.

Richard Jones then brought one back into Blackwell's pads and the young seamer struck again soon after lunch when Phil Mustard (25) attempted to drive and edged to Davies.

A more positive approach developed as Chanderpaul matched Liam Plunkett run for run in a stand of 103 in 27 overs before Worcestershire found some relief with two wickets in quick succession.

Having hit eight fours in his 52, Plunkett hoisted a ball from Daryl Mitchell towards deep mid-wicket, where David Wheeldon dived forward to hold the catch, and Davies claimed another dismissal from Mitchell Claydon's leg-side waft at a loose delivery by Whelan.

Mark Davies (16 not out) escorted Chanderpaul to his double hundred and when Worcestershire were finally released from their toils, four bowlers had conceded 100 or more runs.