His loyalties are divided between the Highlanders and the Hurricanes - he grew up as a rugby-obsessed youth in Dunedin, but has lived in Wellington Central for 20 years and is now the electorate's MP.
"I am very torn and I would be happy whichever team wins," he said yesterday.
He once half-joked that if he had been on Mastermind his subject would have been Otago rugby in the 1980s.
"I grew up at Carisbrook watching rugby. That's what I did as a child. I lived less than a kilometre away."
Then, Otago were a team of battlers under coach Laurie Mains.
At the age of 11, in 1983, Mr Robertson won the honour of being ball-boy at an All Blacks test against the Lions that was played in such cold temperatures that some of the New Zealand players wore fingerless gloves.
The home team won 15 to 8 in a game in which Stu Wilson set a record -- long eclipsed -- for the number of tries scored by an All Black.
"The way I look at it is I support both the Hurricanes and the Highlanders," Mr Robertson said.
"If it is NPC and it's Otago, I tend to support Otago more because that's who I grew up watching.
"But with Super Rugby, if I have to choose, if you're making me choose, then the whole time the Hurricanes have existed I've lived in Wellington."
So it's Hurricanes?
"By a sliver, by a hair's breadth," said Mr Robertson, who is Labour's finance spokesman.
Both teams have been in a Super Rugby final, the Highlanders in 1999 and the Hurricanes in 2006, but both lost to the Crusaders.
Deputy Prime Minister and Finance Minister Bill English, who was brought up in rural Dipton, Southland, but lives in Wellington is unequivocal: "Highlanders."
And he has local connections. "One of their stalwarts of recent years, and a key to their recovery, has been John Hardie from Dipton, a loose forward.
"He is Dipton's most famous son," Mr English said modestly.
Not the second most?
"No, no. Most famous. He is respected. I am tolerated."
- Audrey Young of the New Zealand Herald
