Australia's bowlers, led by the fearsome Johnson, earned themselves an extra day's break before Thursday's second Test in Port Elizabeth by dismissing the Proteas for 200 in the last session of day four. Johnson's three wickets with the new ball in the second innings ensured they never threatened to reach the Test-record target of 482 they had been set to win the match.

Captain Clarke said the win in Centurion, Australia's first in its past 10 overseas Tests, matched its best performances during the Ashes.

"A lot of credit has to go to our batters. That was quite a nasty wicket, to be honest, and I would've hated to see any team having to bat on on day five," he said.

"You saw me declare after three-and-a-half overs. That certainly wasn't the plan when I walked out to bat today but I'd seen enough in that wicket in three-and-a-half overs to think it was going to be quite dangerous to bat on."

Clarke agreed the unbridled hostility of Johnson, and the Proteas' inability to handle his bowling, had been a key factor in Australia's victory.

"Obviously Mitch was outstanding, once again," he said.

"I don't know what South Africa is feeling right now. I know there is not one cricket lover around the world that doesn't know Mitchell Johnson is bowling at 150km/h and executing his skills better than any other bowler in the world.

"He's the fastest bowler in the world at the moment, there's no doubt about it, but his execution and his skills are as good as any other bowler's.

"It's an amazing skill to be able to bowl fast, but it's being able to hit that mark as often as Mitchell is. That's class - that's world class."

Johnson's career-best 12-127 ranks ninth for Test hauls by Australian paceman, and was the most prolific by any Test paceman since Indian left-armer Irfan Pathan's 12-126 against Zimbabwe in 2005-06.

The performance also earned him the Man of the Match award, his fourth in his past six Tests.

Johnson insisted he could still improve on his performance from Centurion Park, but acknowledged he had "felt pretty good out there today" and "will look back on at the end of my career and be proud of that moment."

Johnson believed he had developed a "fear factor" among certain batsmen in recent months.

"It's been a fairly big part especially on wickets that have suited that kind of bowling like it did out here," Johnson said.

South African captain Graeme Smith, a victim of Johnson in each innings, denied the left-armer had rattled the South African batsmen, but acknowledged "no doubt he was the difference in this game".

He said the Proteas batsmen needed to create a way to resist him. But he also intimated he doubted Johnson would be as effective at Port Elizabeth, which typically favours spin more than pace, than he was at Centurion.

"I think the surface suited his style of bowling here. He got a lot of difficult bounce, he got a lot of balls to get really big on batters in good areas, which made it obviously very tough. But it's not long ago that we can think back to big moments in games where we've been able to put him under pressure," he said.

Australia captain Clarke said he was particularly pleased that his players remained focus because the series result was still in the balance.

"We take nothing for granted in this team. We'll turn up for training in two days' time and it will be like we haven't bowled a ball yet in this Test series.

"We want to get back to being the number-one Test team in the world. We're a long way from that at the moment but it's nice to see us compete against the number-one team and challenge ourselves."

Australia will have a rest day in Johannesburg on Sunday before flying to Port Elizabeth on Monday.