The day began with Peter Trego claiming his fifty early on, from 46 deliveries, including nine boundaries and Somerset were 284-5 when he was eventually bowled by Liam Plunkett on 69.
A single from Hildreth just after his fifty (from 93 balls, including six boundaries) pushed Somerset past the 300 mark.
Two wickets in two balls from Ben Harmison, both Buttler (39) and Phillips (0) out lbw, signalled the lunch break at which Somerset were 348-7.
A couple of rain breaks delayed play but not significantly enough to reduce overs. James Hildreth persevered to pass the hundred mark, which included a fifty partnership with Afonso Thomas. Hildreth then became Ruel Brathwaites first wicket for Durham when he was bowled on 105.
Brathwaite cleared up the tail, bowling Thomas on 26 and in the same over Kartik (11) was caught by Blackwell signalling the end of Somerset’s first innings, 426 having established a lead of 140.
Ben Phillips struck in the eighth over of Durham’s second innings, trapping Mark Stoneman lbw on 16 as the hosts reached 33.
Michael Di Venuto and Gordon Muchall pushed Durham to the hundred mark by the 24th over and went on to record a hundred partnership.
Trego claimed the only other wicket before the close, bowling Muchall on 33 in the 38th over as Durham stood at 146-2. Durham passed the 150, clearing any Somerset lead with ten overs remaining before the close.
At the end of day three Durham were 171-2, with a lead of 31, Di Venuto 84* and Harmison 2*.
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At the close of play we spoke to Ben Harmison after his four wicket haul from the innings, “It was horrible out there at the start but it got easier as the day progressed and when I got the end that I wanted. It was tough but I thought Hildreth batted excellently. Somerset are at the top for a good reason, they’re a good team, having Marcus Trescothick opening and then good batting all the way down to seven, especially by the time we’re got the soft ball, is tough opposition.
“We’re here to spoil the party if you like, we’re not here to roll over for anyone, we’re upbeat, we’re going to try and put as big a score as we can on the table and hopefully bat all day if we can. Diva batted brilliantly, even just being out there with him for ten overs tonight, he’s so calm he really gets you through. I hope he gets a massive score tomorrow and that I can be with him for most of the day. I didn’t get my hundred last week so I wouldn’t mind knuckling down and getting some runs. If we can get a lead of 150 I think that might be enough, Scott Borthwick didn’t get a bowl in the first innings and there are a lot of rough patches now so I think he’ll come into play more with Ian [Blackwell].
“It’s been a tough season but we’d like to end on a high and take that momentum over to next year. “