Mark Leibler sits alone in his office at Arnold Bloch Leibler, the law firm where he's been a partner since 1969. It's in the magnificent former Commercial Banking Company building on Melbourne’s Collins Street. He’s wearing an open white shirt, grey trousers and black shoes. Like other 76-year-old men used to a career working in offices, he ruminates about the challenge of remembering how to knot a tie in this tieless age.

The father of four and grandfather of 14 is an expert in tax law, and many of his clients populate the upper reaches of the Financial Review Rich List; he's also a prominent leader in the Australian Jewish community. However, it's his behind the scenes influence that marks him out. It stretches right to the top of major Australian company boardrooms, through the Australian Tax Office (ATO), to the apex of this country's and Israeli politics, including a close relationship with Israel’s powerful intelligence agency, Mossad.