Surrey 106 (Norton 5-50) and 398 for 9 (Burns 115, Pope 73, Hadley 3-69) lead Glamorgan 358 (Crane 106, Cooke 101, Atkinson 4-61) by 145 runs
Rory Burns' century gave Surrey a fighting chance after being made to follow on against Glamorgan.
Surrey's captain played a timely knock to make 115, his first century of the season, making sure the hosts will have to bat again on day four to force a result. Surrey ended a day on which just seven wickets fell on 398 for 9, as the pitch offered little for bowlers in the blazing sunshine.
Surrey's two nightwatchers allowed for a lengthened batting order with Tom Lawes - Gus Atkinson's replacement - and Jordan Clark following Ryan Patel and Adam Thomas in the final four positions of the order.
Ryan Hadley's 3 for 69 was the stand out for Glamorgan, removing Patel and Thomas late on a long summer solstice day, but the visitors continued to frustrate with Clark and Lawes adding an unbeaten 56 for the final wicket by the close.
The sun beating down on Sophia Gardens, a 30-over old ball and Timm van der Gugten being leant on with ease at 11am was a sign of a long day in the field for Glamorgan. One positive was Mason Crane, who bowled the first over from the Cathedral Road end, getting significant turn from the outset on day three. One particular delivery early on in the day went for byes between Chris Cooke and Sean Dickson at first slip.
Surrey's nightwatcher Rahul Chahar helped to combine with Burns for 76 with two straight sixes off Crane's tossed-up leggies. The Surrey captain was allowed to then pass 50 with ease and build towards a first century since August 2024 with three sweeps in the over against the legspinner.
Although Chahar fell to Ben Kellaway's offspin, and Dan Lawrence was bowled driving at Hadley, Burns and Ollie Pope dug in for more than 35 overs.
The new ball still troubled very little until Burns flicked a wayward Tom Norton delivery behind, only for Sam Curran to pay for a second poor display of footwork to be removed for 1 after a first-innings duck.
With wickets falling in pairs, it was time for another partnership to follow the century added from Burns and Pope. The latter stuck out with Patel to improve on his first-innings work until he was next to fall softly, chipping Crane to mid-off straight after tea.
Another double breakthrough came with Thomas and Patel both falling while set to Hadley in his final Glamorgan outing. It was a fitting way for his efforts to end, but Clark and Lawes resisted for the final 12 overs to give Surrey a sniff of an upset on the final day.
