Paul Collingwood hit his 20th first class century for Durham to help them take control on the second day of the LV=County Championship match with Somerset at Taunton.
The skipper followed up his five wickets on the first day by hitting an unbeaten 109 in a total of 380, which saw Scott Borthwick contribute 94 and Michael Richardson 59 as their side grabbed a first innings lead of 81.
Lewis Gregory was the most successful Somerset bowler with five for 99 from 21 overs. By the close the hosts had crumbled to 54 for four in their second innings and still trailed by 27.
Durham began the day on 98 for two in reply to 299. Borthwick was on 52 and Richardson soon followed him to a half-century off 61 balls, with 6 fours.
The pair had taken the score to 157 when Richardson dabbed at a wide ball from Gregory and edged to wicketkeeper Alex Barrow.
Borthwick had faced 110 balls, hitting 17 fours and looking largely untroubled, by the time he fell lbw, trying to work a good length ball from Jamie Overton through the leg side with the total on 190.
Lunch was taken at 224 for four with Calum MacLeod unbeaten on 39. He helped Collingwood add 48 before playing across the line to Tim Groenewald and falling for 44.
It was 280 for six when Phil Mustard was caught behind for 22 defending a ball from Peter Trego. A crucial moment followed when Barrow spilled a chance offered by Collingwood, on 46, off Gregory.
Collingwood quickly went on to an 88-ball half-century and by tea Durham were 347 for six, the new ball having been taken at 335 for six.
Paul Coughlin and John Hastings fell to Gregory and Groenewald respectively soon after the interval, forcing Collingwood to attack with the tail.
Approaching his 39th birthday, the former England player showed he still has plenty to offer, bringing up his century by advancing down the pitch and pulling Gregory for his 11th four. There were also two sixes in a hugely valuable knock, ended by the fall of the last two wickets at the other end.
Somerset were left with 20 overs to face in the day and lost captain Marcus Trescothick cheaply for the second time in the match as he was bowled by Chris Rushworth with the first ball of the fourth over.
Rushworth quickly followed up by pinning first innings centurion Johann Myburgh lbw for nine, while Graham Onions had Tom Cooper caught behind for five to make it 18 for three.
James Hildreth was well caught by the diving Borthwick in the slips, driving at Rushworth, for eight with his team still 55 behind