"He is getting bigger -- it shows you what you can still do even when you're in your eighties," said Lunn, who worked for Melbourne-born Murdoch for 17 years.
Speculation about Murdoch's retirement and succession planning has been rife for years, but indications are that the billionaire father-of-six intends to keep working at the empire he built from a single Adelaide afternoon paper.
"I had lunch with him recently," Kelvin MacKenzie, the former editor of Murdoch's British tabloid The Sun, told The Guardian newspaper. "He was going on about iPad this and Internet that. I think he's 80 going on 18."
Comments on his age are reportedly unwelcome, but Murdoch has crammed much into his eight decades -- creating a business with interests stretching from Australia to Europe, the United States, Asia and Latin America.
Born into a patrician family headed by his newspaper proprietor father, Sir Keith Murdoch, he is frequently reviled by critics who slam his politically-conservative dominance of the global news market and blame him for the excesses of tabloid media.
But he is revered in equal measure by his staff and respected by opponents.
Acquisition and expansion, and a formidable capacity to manage debt, have characterised his career.
Out of his Australian newspaper assets, including his launching of the national broadsheet The Australian in 1964, grew a global media empire.
In the late 1960s, he moved to London where he acquired more mastheads, including News of the World and The Sun and later The Times, changing the face and landscape of the British media and outraging traditional proprietors.
In the 1980s, he fought a bitter industrial dispute over his decision to move his papers from their traditional home in Fleet Street to new headquarters in Wapping where electronic production allowed him to slash staff.
Murdoch has always moved around the world to be near his business interests. From Britain, he relocated to the United States where more bold acquisitions followed and where he became a naturalised US citizen in 1985.
By 2010, his News Corp. boasted assets of US$57 billion and annual revenues of about US$33 billion across its television, book publishing, Internet and newspaper businesses, including conservative US media outlets such as Fox television and the Wall Street Journal.
Twice-married Murdoch, known for his flawless manners, has never diversified out of the media businesses -- often taking considerable risks with his buys -- and is often portrayed as a newsman at heart.
Writing in The Guardian, the Sun's former assistant editor Roy Greenslade said News Corp. only existed due to Murdoch's "acute understanding of the media as a business, as a commercial proposition".
"In terms of newspapers, Rupert really is a benevolent dictator," Lunn said.
"He certainly knew and understood newspapers which a lot of people who own and run newspapers don't," Lunn told Australian public broadcaster ABC.
The media proprietor has always surprised, and his bold BSkyB bid is the latest in a long string of unexpected gambles that include his tendency to turn up unannounced in his offices around the world, Lunn said.
"He turns up unexpectedly at your desk," Lunn said. "And Rupert asks you questions... or else he says, 'What's the circulation of your opposition paper?'"
Murdoch is undoubtedly the biggest media name in his home country, dominating newspapers, Internet and cable television, and playing an influential role in national politics.
But as his mother Dame Elisabeth Murdoch, who turned 102 last month, has said, wealth and influence are not everything to everyone.
She said she tells people: "I say, 'I am very proud of him because he's a good father and a good son.' And that's what I'm proud of. Not so proud of his wealth."