William Gummow

The longest-serving member of the High Court of Australia is no judicial rock star. He's rarely mentioned in the press and his biggest Facebook fan club boasts only 162 members compared to Michael Kirby's 5,244. Yet bald and bespectacled Bill Gummow stands out as one of the most influential judges in recent Australian history.

"He would be number one over the past 10 to 15 years in terms of shaping the direction of the court in key cases,"  constitutional law expert George Williams tells The Power Index.

"He wasn't the chief justice but if you wanted to win some of the big cases then you had to have Gummow on your side because it was extremely rare for him to dissent."

Gummow's reputation as the High Court's bellwether is borne out by the statistics. He has dissented three times this year, more than usual, but his long-term track record is formidable. From 2005-2010, he dissented in only seven out of 240 cases – in other words, only 2.9% of the time (at his peak Kirby reached 48%).

And while Kirby was the court's conscientious loner, Gummow is famous as an alliance builder.

Gummow teamed up with Justice Kenneth Hayne so often – and so effectively – that High Court observers took to calling it the "Bill and Ken show". More recently, according to analysis by George Williams and Andrew Lynch, he has formed a potent duo with Chief Justice Robert French.

He's also a fearsome questioner from the bench.

"One needs to have done one's homework because he knows his stuff and can ask penetrating questions," says top barrister David Bennett.

Gummow "used to be quite aggressive in his questioning", Bennett says, but has calmed down over recent years.

"He's got incredible dedication and learning," says legal affairs commentator Richard Ackland. "He will spend all weekend in the library drowning himself in the details of the jurisprudence of a particular case. He brings to it this enormous brain."

Australian Lawyers Alliance President Greg Barns has no doubt: "Gummow is intellectually the most influential member of the high court".

The Dick Cheney lookalike was appointed to the bench by Paul Keating, but is often tagged a conservative. Moderate, however, seems a more apt description: Gummow has no qualms knocking down government policies when he sees fit.

"Gummow has a long history of a very wide, expansive view of judicial power," Greg Craven says. "That has had highly practical effects."

Last year, Gummow was part of a 4-3 majority that ruled it unconstitutional for the electoral roll to be closed on the day election writs are issued. Had he gone the other way, 100,000 Australians would not have been able to vote at the last federal election. He also helped strike down a law which had made it illegal for NSW bikies to associate with one another and was part of the 6-1 majority that declared the Gillard government's controversial "Malaysia solution" illegal.

Those who pigeonhole him as a conservative also tend to overlook his decisions in controversial cases such as Al-Kateb (2004) and Wik (1996). In Al-Kateb, he handed down a rare dissent by arguing that it was unconstitutional for a stateless person to be locked up in detention indefinitely. In Wik he was part of the 4-3 majority that ruled pastoral leases do not extinguish native title rights.

"As much as he's been a force for conservatism, he's also been a force for liberalism," says Richard Ackland.

Gummow, 68, trod a well-worn path to the apex of the Australian legal world. He holds a high-school diploma from Sydney Grammar and obtained first-class honours in arts and law at the University of Sydney. Upon completing his studies he began working at top commercial lawfirm Allen Allen & Hemsley – and it didn't take the bigwigs there long to realise they had a rising star on their hands. Only three years after being hired, Gummow was made a partner and put in charge of a booming practice specialising in banking law, trusts and intellectual property litigation.

But raking in the big corporate bucks was never going to be enough for the theory-obsessed wunderkind. All up, Gummow spent 30 years – from the year of his graduation until his High Court appointment – as a lecturer at the University of Sydney. His 1974 textbook Equity: Doctrines and Remedies is regarded within legal circles as one of the most influential law publications to ever come out of this country.

The unmarried, apparently childless, Sydneysider is extremely guarded about his life away from the court. "He doesn't reveal anything about his personal life at all to anybody," says a legal insider who knows him well. "The law has been his life – but he's also a cultured man. He goes to the opera and he's a voracious reader. He's read virtually everything that's ever been written."

He's also got a wicked sense of humour, according to Justice Dyson Heydon, his fellow High Court judge and friend (Gummow was best man at Heydon's wedding).

"When the young and vigorous Gummow J was appointed in 1995 to replace Mason CJ, on his first day the other [much older] judges held a lunch for him," Heydon recalled in a 2002 speech. "The waiter asked him what he would like. 'Sirloin steak,' he said. The waiter said: 'What about the vegetables?' He replied: 'They can order for themselves'."

Unlike Chief Justice Robert French, who has voiced support for a republic and a treaty with indigenous Australians, next to nothing is known about Gummow's political views. If he gives a speech or writes an article, you can bet it will be about a dry technical issue. He genuinely believes that human rights are best protected by a strict interpretation of the law, not judges bearing their souls.

The 16-year High Court veteran will be forced to step down from the bench when he turns 70 next October. Upon his departure he may finally get the attention – if not the Facebook groupies – he deserves.