When Sir Warwick Fairfax belatedly discovered that his first wife had conducted an affair with Menzies, The Sydney Morning Herald had a rather less passionate affair with Menzies’s opponent, Arthur Calwell.

So claims Mungo MacCallum in an article in the November edition of The Monthly. But how does he know the two had an affair? Was Australia’s longest serving PM really a philanderer? Or is this one of those moments at which rumour and hearsay morphs into “fact” and worms its way onto the public record?

MacCallum has published the claim before (The Age in 2002) and he told Crikey that he heard it from a number of politicians, including Gough Whitlam, and it is well supported.

“It was common knowledge in Canberra. It was known to be fact. The car driver who delivered Menzies to the Point Piper mansion used to boast about it. It wasn’t blurted across the landscape but I think you’ll find most people in the inner circle knew about it.”

But those who’ve studied the history of the period disagree. Gavin Souter, author of two respected biographies of the Fairfax family (Company of Heralds and Heralds and Angels) said he’d investigated the rumoured relationship between Menzies and Dame Elizabeth Fairfax but found nothing to support it:

Menzies appeared to be fond of her company, but there no evidence at all of it being more than platonic with just a bit of attraction involved. I had access to all the archives. I found nothing at all. I didn’t get a chance to ask the Lady herself because she had just died but I did ask her son James and I felt I was on pretty good terms with James Fairfax and if there had been any substance I think he would’ve told me. He gave it a blanket denial. He had no reason to deny it if it was in fact true.

Gerard Henderson, author of Menzies’ Child, is even more blunt: “Mungo is a gossip-monger and he’s thinking with his c-ck. In the late 1950s or 60s a friendship that might lead to a sexual relation might not lead to a friendship in the late 1930s. You can’t transpose current mores onto past mores.”

According to Henderson the only evidence of a relationship between Menzies and Betty Fairfax is a letter he wrote to her in 1938 saying he might come round for a drink. He also said he discussed the letter with Menzies biographer Allan Martin before he died and Martin also said he could find no evidence to support claims of an affair.

“Martin went off evidence. He was an incredibly practical historian,” says Henderson. “You’d think if Menzies was worried about this, why would he leave that letter in his own papers? This is just ludicrous. I don’t know what goes on in Byron Bay but it’s not the way the world works elsewhere.”

Monthly editor Sally Warhaft told Crikey she’d checked the claim before publishing but would re-examine the evidence and publish a correction (online only) if she concluded it was warranted.

“I spoke to Mungo about this. When I first read it I said I felt very uneasy about it. He said he’d talked to a lot of people and it was common knowledge and he’d published it before. I accepted Mungo’s insistence that his sources were strong.”