Peter Trego smashed the fastest first-class century of the season so far to give Somerset hopes of a first LV County Championship victory of the year against Lancashire at Old Trafford.

The 28-year-old all-rounder took only 83 balls to reach three figures, and shared a sixth-wicket partnership of 186 in only 32 overs with James Hildreth, who was out for 99.

Somerset had been in trouble at 157 for five when they came together in reply to Lancashire's first innings total of 292, but ended with a lead of 91 despite losing their last five wickets for 40.

However they were frustrated when bad light then rain prevented any play after 4.30pm, when Lancashire had reached 32 without loss in their second innings.

Resuming the third day on 155 for four, Somerset had quickly lost their young wicketkeeper Jos Buttler, who lost his off stump shouldering arms at Glen Chapple.

But Trego, who had already hit two half centuries in five previous Championship innings this season, played positively from the start.

He made Lancashire pay for dropping two straightforward chances, when he was 22 and 40, with Daren Powell the unlucky bowler on each occasion.

He reached 50 from 57 balls with eight fours, and raced to the eighth first-class century of his career from only another 26 deliveries, overtaking Hildreth in the process.

Powell finally dismissed him, caught off a top-edged pull, for 108 from 88 balls, with a total of 17 fours.

Hildreth fell agonisingly short of the century he richly deserved when he was caught behind pushed nervously at Chapple, although the 25-year-old could take consolation from a welcome return to form after a scratchy start to the season.

Chapple also dismissed Damien Wright after a quick 18 to claim his third wicket although they were expensive, as he went for 146. Michael Munday went cheaply to Powell, and Kyle Hogg returned to have Alfonso Thomas caught off a top edge and complete figures of four for 96.

But Lancashire badly missed Sajid Mahmood, who was again unable to bowl after suffering a calf strain when batting on Tuesday.