What did Michael Clarke say to Dale Steyn on the final day of the Cape Town Test, which so offended the South African pace great that he still holds a grudge months later?

What is said on the field usually stays there, but respected and well-connected South African cricket writer and broadcaster Neil Manthorp believes he knows the answer.

In a Q&A segment on the Supersport website after the Proteas defeated Australia in the triangular series final in Zimbabwe, Manthorp said: "I believe Clarke basically called Steyn a "cheat" in the closing stages of the Cape Town Test match. You can call Steyn pretty much any name under the sun and it will be water off a duck's back, but don't call him a cheat!"

We might never know exactly what was said, but the fallout continues with a dispute over whether or not the Australian captain apologised. Clarke believes he has, both in person and at his press conference, and Cricket Australia's digital news site this week published footage that backs the skipper's version of a conciliatory exchange as the pair shook hands after the Test.

"As the teams shook hands after Australia's series-clinching victory in the late afternoon Cape Town sun, Clarke stopped for an extended chat with Steyn and was overheard to say "sorry" directly to the Proteas paceman," an accompanying story on the CA website said.

"Clarke's handshake was enthusiastic, accompanied by an apologetic smile and shake of the head. Australia's captain did most of the talking in the exchange as he gripped Steyn's hand, his left arm around the bowler's shoulder.

"Steyn's reply drew a smile from vice-captain Brad Haddin, who was waiting in line behind Clarke. With a nod of his head and a pat on Clarke's shoulder, Steyn also appears to accept Clarke's sentiment before the pair part and the line-up moves forward again.

"The footage could embarrass the South African, raising the question did Steyn simply forget this exchange following a bitter Test defeat for the Proteas, or are other motives at play."

The Proteas have made no attempt to play down the tensions between the sides, who will clash again in a limited-overs series in Australia in November.

One-day captain AB de Villiers said there was "lots of personal stuff" during the March Test series. "I see that it's part of the game," de Villiers said. "But they can't expect us to be mates with them off the field then, if they get very personal."

David Warner has admitted he overstepped the mark when he suggested the South Africans, and de Villiers in particular, had used questionable methods to gain reverse swing at Port Elizabeth, where Steyn tore through the Australians.

The catalyst for the Cape Town incident was Vernon Philander's controversial DRS reprieve after he gloved a catch to short leg as the Australians strained for victory. Fast bowler James Pattinson, who said something to Steyn before Clarke got involved, offered this version of events in an interview with Fairfax Media in June.

"Just a little bit of argy bargy. It's good having the captain stick up for you... I love watching Dale Steyn bowl so it was nothing personal against him. It was just in that moment of the game, when that decision didn't go our way you look back towards Adelaide [in 2012, when Faf du Plessis forced a draw] and think, 'Is that going to happen again?'... He [Steyn] was having a go about the way we talk to the umpires, and I just told him that he always does it so why is he whinging about it?"

Clarke's public apology included the admission he was "out of line ... to a player I have the utmost respect for, who tries to kill me every time I bat – who batted exceptionally well".

But Steyn was in an unforgiving mood after taking 4-35 in the triangular series final in Harare, by which time Clarke was home nursing a hamstring injury.

"I don't take many things personally, but what he did say to me I did take personally," he said. "I know he apologised in the media and I should be playing this down. But the day he comes and shakes my hand and says 'I really mean what I said' and behaves like the way he should, maybe then I will [forgive him]. But for right now, he's not here so I'll wait until I get to Australia."