The Routemaster 1660 was once just another bus in a fleet of two-storeyed giants on the streets of London - in this case, the Number 12 Piccadilly Line.
The Routemaster is now operated by Connectabus for sightseeing tours.
The company's managing director, Ewen McCammon, is proud of the flagship vehicle.
"In 1984 it was brought over to New Zealand by a few guys.
They operated it for quite a few years through Simulate, then CityBus.
Then Connectabus bought it off them about 10 years ago.
It's the only one working commercially like this. It's a classic now."
Using technology developed during World War 2 in factories making spitfire aeroplanes, the bus was built in 1963.
It was very advanced for the time, Mr McCammon said.
"They would have brought it [to New Zealand] on top of a freight ship ...
One guy turned up and said he used to work on this bus in the UK.
The exact same bus.
It was built in 1963 so it was operating in the UK for quite a number of years, and after that it was brought to New Zealand."
Driver of the double-decker Peter Harrex said the bus handled reasonably well.
"It's pretty good on the whole.
It sits on the road very nicely."
It was sometimes difficult getting replacement parts from overseas but for an old machine, the bus was quite reliable, Mr McCammon said.
"We have our problems from time to time, but we just rebuild the engine and the transmission's been done ...
You just have to keep refurbishing them and they'll be fine, as long as you can still get enough parts for the engine and the transmission."
Decommissioned buses like the 1660 were used for sightseeing worldwide, and bus-spotters from all over the globe came to see this one, he said.
"Visitors are actually increasing on the double-decker."
