Walter’s dismissal at 248-3, leg-before to Sean Abbott after facing 184 balls and hitting 14 fours, was quickly followed by the wickets of Charlie Allison for 40, Matt Critchley for eight and Michael Pepper for 17.
Allison was leg-before to Matt Fisher and Critchley held at the second attempt by Rory Burns at first slip off Tom Lawes.
Those three wickets were all taken with the old ball, before Gus Atkinson removed Pepper with the second new ball.
Walter, a late developer as a cricketer, did not score his maiden first-class hundred until he was 27 but now – at 31 – has matured into one of the domestic game’s most consistent top-order players.
His sixth Championship century was completed just after tea, with an off-driven four as Surrey belatedly introduced Dan Lawrence’s off-spin, and it should not be forgotten that when Walter signed professional terms with Essex in 2016 at the age of 22, he was viewed as a bowling all-rounder who batted in the lower order.
Surrey’s best chance to break the Walter-Elgar partnership did not come until 138 runs were on the board, but Abbott spilled a caught and bowled opportunity when Walter, on 53, mishit one straight back to him.
An Oval crowd which swelled to 5,700 under cloudless blue skies saw Atkinson take the new ball in his first competitive match since last December’s Boxing Day Ashes Test in Melbourne, his initial six-over spell conceding only 18 runs.
Atkinson bowled sharply at times but had to wait until his 18th over for his first wicket, a nip-backer beating Pepper’s defences after the Essex keeper had added a useful 47 with Thain.
For the first 24 overs, Surrey’s seamers operated as a pack from around the wicket to the two left-handed openers but Elgar and Walter were more than equal to the tactic.
Abbott’s drop also meant they had to wait until the 47th over for the breakthrough, which came when Jordan Clark – from over the wicket – had Elgar caught at the wicket by Ben Foakes with one angled across him.
Tom Westley, back after a two-match absence with a damaged finger, struggled for 27 balls over his single run before bottom-edging an attempted pull at Lawes into his stumps.
That was 194-2 but Walter and Allison then added 54 for the third wicket either side of tea to frustrate Surrey further.
Burns’ team were rewarded for their collective resolve, however, during a final session that saw them bowl themselves back into a game that promises to be a hard-fought affair.
Report by ECB Reporters’ Network, supported by Rothesay.
