Australia found an unlikely batting hero in Scott Boland, but his gritty Test best was neutralised by a sensational spell by Wiaan Mulder, who helped pull off a dramatic win for South Africa in the rain-hit St George’s Park Test.

Boland’s 166-ball resistance ended when Mulder nipped one into him, perfectly missing his defence to rattle his stumps. It snipped the last piece of Australia’s defiance, built bit-by-bit by Boland, but anchored by Travis Head’s century.

The 37-year-old Boland had come in the previous evening to partner Head with Australia in a bit of strife, dead-batting 23 balls for two runs by stumps. But his duties as a nightwatch turned into a full-fledged responsibility on Day 5. Rain, which had ravaged much of the first two days, returned to eat up the first session.

It delayed the second new ball for South Africa, who were also without the injured Anrich Nortje.

The first phase was all about survival for Australia. Near-perfect deliveries from Kagiso Rabada whizzed past the outside edge and the off-stump. Simon Harmer had a crowd around Boland to entice an edge. Head, already on the cusp of a century going into the final day, ticked past that landmark. It was only his second overseas Test century, and his first in over three years.

Boland’s block-a-thon had some lively moments too. Against Rabada, and with a slip cordon, he pulled off an audacious ramp. He also slapped and sliced deliveries with extra width past point.

But it was trumped by Mulder’s nagging accuracy, bowling with the keeper up, and seaming it off a pitch that also had the odd sharp turn for spinners. He first gave South Africa a post-drinks breakthrough when Head tried to climb the bounce, but chopped it on to his stumps.

Mulder didn’t leave that ploy to incessantly attack the stumps, perfectly complementing Rabada, armed with a second new ball soon after.

Steve Smith, down to No.7 due to his neck issue, got out to a bizarre top-edge, induced while chasing a wide bouncer from Rabada off the new cherry. Matthew Breetzke caught it after a slight fumble. Temba Bavuma, in the distance, had his back turned, hoping it wasn’t a spill.

Boland then joined forces with Alex Carey to push the visitors into the final session. But the magic touch from Mulder ended his valiant knock, the third-longest innings by an Australian nightwatch ever.

Pat Cummins had played two vastly contrasting knocks in the first Test, but none of those runs mattered against a rampaging Mulder. The one to Boland had wobbled in; against Cummins, another escaped the outside edge and knocked the top of off stump. Down to eight, Australia were quickly seeing their hopes fade away.

To add a little more drama, dark clouds started wafting in from one side. But there was no rain. Rabada was quickly pressed into action and did his bit with a full ball to floor Starc, who had built a short stand with Carey until then. Marco Jansen completed the final act: a loose slash from Josh Hazlewood flew to the slips, giving Jansen his lone scalp of the innings and sparking victory celebrations.

It was the first time since 1970 that South Africa had beaten Australia after enforcing a follow-on. It also gave them only their fourth innings win against Australia.

Brief scores: South Africa 425/9 decl beat Australia 99 & 295 f/o (Travis Head 121, Scott Boland 40; Kagiso Rabada 4-77, Wiaan Mulder 3-64) by an innings and 31 runs.