WILL Smith led the way with a gritty innings of 80 before Ian Blackwell and Phil Mustard capitalised to put Durham in an almost unassailable position.
But after a fluent stand of 72 with Blackwell, Mustard played on for 32 in the over before tea, leaving Durham on 280 for six, 175 ahead.
Durham defied the testing conditions to lose only one wicket in the morning when Gordon Muchall fell 15 minutes before lunch for 28, caught at square leg off Dominic Cork.
With left-armer James Tomlinson swinging the ball into the right-handers, a tough first hour produced only 18 runs before Muchall pulled Sean Ervine for four.
When leg-spinner Imran Tahir came on Smith pulled him for two fours in one over to reach 50 off 170 balls and he accelerated after lunch as Tahir continued to bowl too short.
Just when it was all beginning to look a little too easy, however, he snared Dale Benkenstein for 22 when the ex-captain top-edged a sweep to backward square leg.
Smith fell lbw to seamer David Griffiths five overs later, but Blackwell continued to underline that he is a much more accomplished four-day than one-day player.
He was off the mark rather streakily with a carve over the slips off Griffiths, but then eased his way to 50 off 60 balls without appearing in any hurry. He was unbeaten on 51 at tea.
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