|LV= County Championship Division Two, Colwyn Bay|
|Close, day two: Glamorgan 232, Surrey 400-5|
|Glamorgan 2pts, Surrey 7pts|
Surrey opener Zafar Ansari compiled his second century of the summer as they built a 168-run lead against Glamorgan on day two at Colwyn Bay.
The left-hander made 112 and passed 700 Championship runs for the season in the process before falling to Jim Allenby.
He shared an opening stand of 182 with Rory Burns, who fell for 97, and also put on 88 with Arun Harinath (60).
Michael Hogan removed Harinath and Vikram Solanki with successive balls, but Surrey were 400-5 at stumps.
Having bowled out Glamorgan for 232, the third-placed visitors were already in the driving seat at the start of play, and it looked like they might pass the Welsh county's total without loss until teenager Ruaidhri Smith had Burns caught by Jacques Rudolph from a top-edged pull.
Harinath has had a relatively lean time with the bat, but hit a six and seven fours to pass fifty for only the second time this season as he took the leading role in his partnership with Ansari.
However, he edged to Rudolph at second slip when Hogan took the second new ball and Solanki followed in similar fashion after attempting to drive, with Chris Cooke taking the catch.
Allenby had Steven Davies lbw for 37 before a rain interruption with Surrey on 323-4 and later brought Ansari's 408-minute innings to an end by forcing him to play on.
In-form Jason Roy, who hit 10 fours in his unbeaten 59 off 58 balls, and Gary Wilson (16 not out) added 55 to see Surrey through to the close.