We got talking because I'm a cowardly flier and it was windy, and conversation takes my mind off turbulence. And it transpired Hansford and I were blood brothers as yet unmet.
He wrote about science and environmental issues, and I realised I'd read many of his pieces in the past. They were calm, clear, compassionate, well argued - the ordered outpourings of a tidy mind.
But on this particular day, he looked weary, frazzled, a bit of a wreck. "I've just written a book," he said. "And when it comes out, there's going to be one hell of a s---storm."
I hope Hansford has a good raincoat, because that book is now on the shelves, and I imagine he's already being bombarded with kaka.
Protecting Paradise: 1080 and the Fight to Save New Zealand's Wildlife is an overdue corrective to all the misinformation that science-deniers have been spreading on this issue for years.
In spare, unexpectedly poetic prose, Hansford makes the case that 1080 is a crucial tool for protecting our nation's biodiversity and preventing further catastrophic loss of native bird populations.
Every year, rats, stoats, possums and other introduced predators devour the eggs and chicks of more than 25 million native birds. Aerial pest control is essential in the fightback, he writes, which is why DoC reluctantly uses it.
One by one, these persistent myths are refuted, both in Hansford's book and in a series of short videos here: www.protectingparadise.co.nz. Unswayed by a mountain of contrary evidence, the poison's opponents claim 1080 kills more birds than it saves and dispatches huge numbers of deer, fish and frogs; that it builds up to harmful concentrations in our waterways and food chain; that we could trap predators instead and get similar outcomes.
Hansford readily admits that he, too, would rather we didn't have to spread poison through our most pest-ravaged forests, but we have little choice. Either we use 1080, or a lot more of our native wildlife vanishes forever.
A keen tramper and kayaker, Hansford was alarmed by the misinformation that hampered the national conversation around pest control in general and 1080 in particular.
This was a matter of great urgency, he said. Many of our native species were now in such dire straits, we might be the last generation with the chance to save them and give our ravaged ecosystems a chance to heal.
And so Hansford did his part, writing a pro-1080 book he knew would unleash fury in some quarters. As we sat on that plane, buffeted by the strong winds, I applauded his courage.
We owe this man a debt of gratitude for braving such a s---storm in defence of our native wildlife. The least we can do is buy his book so he can afford a decent raincoat.