A VINTAGE Peter Trego century helped Somerset stay firmly on course for the Royal London One-Day Cup quarter-finals with a four-wicket South Group win over Middlesex at Taunton.

The visitors posted 296 for nine after losing the toss - Nick Gubbins making 89 off 78 balls, Paul Stirling 58 and James Fuller a rapid 42 not out. There were two wickets each for Trego and Roelof van der Merwe.

In reply, Somerset reached 297 for six with an over to spare, Trego hitting nine fours and a six in his 104, while Lewis Gregory contributed 69 and Van der Merwe 41. Ollie Rayner was the pick of the Middlesex attack with two for 40.

The result put Somerset on nine points from six group games, while their opponents remain on six.

Middlesex had been given a solid start by Stirling and Ryan Higgins, who took the total to 83 in the 18th over before Higgins, on 39, drove a catch to cover off Trego.

Stirling moved to his half-century off 60 balls, with six fours, before being second man out in the 24th over, caught at deep cover off Trego, who strangely bowled only six overs for figures of two for 27.

Gubbins hit the first six of the innings off Craig Overton in the 25th over, but Middlesex could never put a charge on against some accurate Somerset bowling.

It was 143 for three in the 30th over when Eoin Morgan was caught at mid-on by Trego after top-edging a pull shot off Lewis Gregory and 173 for four when George Bailey drove a catch to cover off Van der Merwe. By then Somerset had used eight different bowlers.

Gubbins reached his half-century off 47 balls and shared a fifth-wicket stand of 58 with John Simpson, who was bowled for 27, looking to reverse sweep Van der Merwe.

James Franklin went quickly to Overton before Gubbins' innings ended when he guided a Tim Groenewald full-toss straight to James Hildreth at short fine-leg.

Fuller provided some late acceleration with successive sixes off Groenewald, but a couple of late run-outs left Middlesex short of the 300-mark.

Somerset would have been happy at the halfway stage but skipper Jim Allenby went for a duck to James Harris when they replied and Johann Myburgh, having looked in prime form moving to 22, had to retire hurt with a side injury.

Mahela Jayawardene (28) helped Trego add 63 before being well caught one-handed above his head by Morgan at mid-wicket off Rayner. And it was 117 for three when Hildreth, on nine, tamely chipped a catch to mid-wicket off Higgins.

Trego had reached a 53-ball half-century against a Middlesex attack deprived of Fuller because of a side strain. Gregory provided excellent support in a fourth-wicket partnership of 86 in 15 overs and the hosts looked well placed when 35-year-old Trego moved confidently to three figures off 106 balls in the 36th over.

He was bowled, advancing down the track to Rayner. But Gregory and Van der Merwe were both dropped in the 41st over, bowled by Harris, with Morgan and Tim Murtagh the culprits.

They proved expensive errors as Gregory reached his half-century off 64 balls and the pair took their side to the verge of victory with a stand of 71 in 8.5 overs before both fell in the closing overs. Josh Davey and Overton completed the job.