"Whangarei was," Potham says, "one of the last regions in New Zealand to have its own art gallery. And even now many people don't know it's here."
Surrounding Sperrey's two works are many more colonial paintings from the Arboretum Trust, a collection assembled over 25 years by an anonymous expatriate collector.
The collection is focused on the works of lesser known artists who were in New Zealand during the early years of European settlement, and gives fascinating insights into the landscapes - including possibly the first painting of Wellington Harbour - Maori lifestyle, fledgling settlements and early colonists of the time.
Potham says the collection was going to a planned new art gallery on Auckland's North Shore, but when the Super City merger scuppered that plan the owners opted for the Whangarei Art Museum.
"That's a loss to the North Shore but a huge coup for Whangarei," says Potham.
"This is a remarkable collection. It would be impossible to overstate its significance from an art history perspective. It allows us to offer a unique perspective of the development of New Zealand art."
In an adjoining display area Potham has curated a Papua New Guinea exhibition of the sort he intends to be a feature of the art museum, mixing modern paintings with traditional masks, pots and ornaments to provide a broader view than offered by a traditional art gallery.
"This is," he says forcefully, "not an art gallery. That's a rather patronising colonial concept. What we've created is an art museum."
And a lot more art is on offer in the Town Basin area, where the new museum is situated.
A short distance away on the banks of the Hatea River is Reyburn House, built in the 1860s by an early settler, and today home of the Northland Society of Arts, which offers an interest mix of works by Northland artists.
Running along the banks of the river is a sculpture trail - including an iron totem pole with images of fish, a giant rope sculpture based on a traditional eel pot, a field of whales' tails and a forest of steel canopies cut with fern shapes - leading to the tip of the little Hihihaua Peninsula.
There the trail culminates with a work entitled Waka and Wave, produced by traditional carver Wallace Heteraka and sculptor Chris Booth.
But Whangarei's dramatic arts scene doesn't stop there. One of the buildings near the town basin is a rather boring steel and glass affair originally built for the Northland Regional Council.
And in the foyer of the art museum is a colourful model based on a concept by the Australian artist Friedensreich Hundertwasser - designer of the famous Kawakawa toilets - aimed at transforming the former home for bureaucrats into an art centre.
Hundertwasser, who died in 2000, suggested the idea in 1993 but it didn't proceed. However, now the Whangarei District Council wants to go ahead at an estimated cost of $12.2 million. And this has clearly stirred up a controversy.
All I can say is, if you go up North to check out the Whangarei arts scene, don't mention Hunterwasser. I think even the bold Gilbert Mair might shrink from the passion likely to be stirred up.
Jim Eagles visited Whangarei with help from Destination Northland.