LEWIS Gregory and Dean Elgar both scored vital centuries as Somerset seized the initative against Middlesex on day two at Lord's.

Gregory brought up his maiden First Class ton before eventually being dismissed for 137, while the South African opener continued his superb early-season form with 158 as the pair added 249 for the sixth wicket.

Josh Davey (47) and Jamie Overton (37) then took Somerset past 400 for the first time this season - though it came too late to claim maximum batting points - before declaring on 443-9, with the hosts ending the day on 42-0 in reply.

Resuming on 161-5 after a rain-affected first day, Elgar and Gregory brought up their century partnership early in the morning session before the latter reached his 50 from 84 balls.

Elgar then brought up his second Championship century of the season with a straight six, which went alongside his 15 fours as he reached the landmark from 186 balls to help his side to lunch at 270/5.

A nudge into the leg side for two then took Gregory to a superb hundred of his own, which was celebrated with gusto, but both batsmen fell before tea - Elgar caught behind, Gregory caught at fine leg - to leave Somerset 387-7 at the interval.

Davey and Overton then combined good running with big hitting to add a valuable 56 for the eighth wicket before Davey was caught at mid-wicket for 47.

Overton smashed two huge sixes on his way to a 31-ball 37 but, when he was caught off the bowling of Ollie Rayner, visiting captain Tom Abell decided to declare with the score on 443-9 - a total that would have seemed unthinkable as Somerset's middle order fell away on day one.

Gregory and Davey were unfortunate not to make a breakthrough as Nick Gubbins and former Somerset man Nick Compton survived some close shaves to see the hosts through to the close, leaving Abell's side looking to ramp up the pressure with early wickets in the morning.