Surrey 406 (Harinath 120, Wagg 4-89) and 276 for 8 (Harinath 104, Hogan 5-44) lead Glamorgan 437 (Wagg 200) by 245 runs

Rory Burns was a welcome sight at Guildford. Wearing two stitches after his horrendous collision with Moises Henriques on Sunday, his spirit seemed unbroken. And he exhibited manifest delight at how his friend Arun Harinath, had so spectacularly capitalised upon his misfortune.

Without Burns' injury, Harinath would not have made Surrey's first team squad, from which he had been absent all season. Yet he has now made history: the first Surrey batsmen since Mark Ramprakash in 2010 to score twin hundreds in a Championship match.

Harinath's first century of the match triggered a moment of unrestrained celebration: "pretty embarrassing," in his own words. He greeted his second ton rather more modestly, removing his helmet and giving a perfunctory acknowledgement to the crowd.

But the grin on his face betrayed his well-earned contentment at an innings more assured than his first innings display. Marked with late cuts of finesse and precision and classy drives through the covers, this was an innings that kept Surrey afloat. In the space of three days - his century came up almost exactly 72 hours away from Burns' injury on Sunday - the career of this affable and well-liked cricketer has been utterly transformed.

And yet his was far from the most memorable innings on the third day at Guildford. That accolade indubitably fell to Graham Wagg who, in an hour of morning bedlam, harrumphed eight sixes to extend his third first-class century and career best to a round 200.

He had arrived at the crease with Glamorgan 106 for 6 and still 300 runs behind Surrey: an innings flirting uncomfortably with ruin. By the time Wagg was dismissed he had not quite ruined Surrey but had certainly ruined Tom Curran's bowling figures: his last four overs haemorrhaged 66 runs.

When Surrey took the official new ball, 11 overs into the morning, they were already on their fifth ball of the day. Four times Wagg heaved Curran over not only the boundary but also the netting designed to protect cars on the Woodbridge Road. Once the ball was kindly returned; three times it was not.

As if to show that he had no personal vendetta against Curran, Wagg also lost a ball against Meaker, this time over the hedges on the other side of the ground. While flat-batted pulls over midwicket were his specialty, there was some sumptuous driving too.

By the time he slapped Meaker to mid-off, Wagg had the first double century by a number eight in Championship cricket since Dominic Cork 15 years ago, and the highest ever score by a Glamorgan batsman outside the top seven to boot.

Together with Michael Hogan, 105 had been ransacked in 67 balls for the tenth wicket, giving Glamorgan full batting points and, quite remarkably, a lead of 31 to boot. That conditions had been overcast only added to the surreal air.

As Surrey replied and the sun emerged, pandemonium made way, very agreeably, for a rather somnolent feel. Compared to Wagg, Harinath's innings seemed almost genteel, yet his innings strike rate of 66 was identical to that of Nasser Hussain in ODI cricket. That statistic is testament not only his unobtrusive accumulation and vigorous running between the wickets, but also the extraordinary manner in which the game has changed in the last decade.

At Ben Foakes looked unperturbed in their third-wicket alliance, it felt as if the Guildford festival was sleepwalking to a draw. It was a rather deceptive notion: Wagg's chutzpah and tremendous skill meant copious time remained in the game for someone to force a result. Foakes edged the persistent, parsimonious Hogan behind, and then Harinath was trapped on the crease against Andrew Salter for 104. When a Hogan delivery jagged back late to defeat Aneesh Kapil the following over, Surrey suddenly led by only 161 with five wickets in hand.

Enter Gary Wilson, who swept freely in a typically resourceful half-century. His dismissal, to a delivery that moved late from Hogan triggered hearty Glamorgan roars. When Gareth Batty followed identically the next over, Hogan's face was a picture of satisfaction, reveling in the excellence of a late evening spell with the old ball. He extracted late movement both ways, and a second five-fer of the season was deserved indeed.

As Glamorgan left the field, buoyed further by Curran's sad but rather inevitable duck - "An absolute disaster from beginning to end today", in the opine of one rather unkind member - they brimmed with satisfaction. Their endeavour should be the prelude to victory tomorrow, which would be fitting reward indeed for Wagg, who rightly led Glamorgan off in spite of Hogan's valour. Yet, with Surrey's lead having reached 245, Harinath's twin tons could yet come in triumph.

"300 would be a great chase - that would be an ideal aim," he reflected. "We know that a last day wicket at Guildford is going to do a bit and help the spinners." So much will be expected of spin twins Batty and Ansari. But whether Chris Tremlett is able to bowl, which remains unclear, feels critical.

Tim Wigmore is a freelance journalist and author of Second XI: Cricket in its Outposts