A SENSATIONAL burst of four wickets in seven balls by Sam Curran rocked Durham before Graham Clark counter-attacked strongly.

Coming in at 83 for five, the Cumbrian hit a 53-ball half-century as he and Mark Stoneman took Durham to 189 for five at tea, leading by 223.

Stoneman frustrated his future employees as he built steadily on a rapid start to reach 90, passing 1,000 championship runs for the fourth successive season.

In nine previous championship innings, Clark had a top score of 36 and three ducks. But he is known as a powerful striker and quickly saw off Curran when he began to drop short.

Durham were 111 ahead on 77 for one when the 18-year-old left-armer returned for a second spell after being given only three overs in his first.

He had not taken a wicket in the match, but Scott Borthwick pushed forward to his second ball and edged to Ben Foakes.

The next ball was slanted across right-hander Jack Burnham, who also edged to the wicketkeeper, then Ben Stokes was able to watch the hat-trick ball pass harmlessly by.

But in trying to withdraw his bat from the next he continued his disappointing match by edging to Kumar Sangakkara at first slip.

Paul Collingwood ran a four to third man but in Curran's next over could only steer a ball rising towards his chest to third slip.

Three balls later Curran could have had another when Jason Roy got his left hand to an edge by Stoneman on 48.

But Curran began to stray, helping Clark off to a confident start, and on 31 he pulled Mark Footitt behind square for a big six.

Two more powerful pulls off Tom Curran followed before Surrey turned to Zafar Ansari.

Clark lofted the left-arm spinner over mid-on for his eighth four to reach 50 and was on 53 at tea.