"I don't like them when they've gone brown like that," I say. "They're squishy and strangely repellant."
"I do," he says. "But I know what you mean. The trouble with fruit is fungus. You go into any house in Scotland and you'll see fruit bowls full of apples and oranges that look like small, furry creatures from Alpha Centauri."
I sense one of his rants coming and edge towards the door. He takes a small sideways step and blocks my escape - he's a big man - then prods me in the chest with a substantial forefinger.
"See the English go on about how we Scots are too stupid to eat right, and have unhealthy diets with fish suppers and deep fried Mars bars, but that's just national stereotypes for cheap laughs."
He shifts his weight from one foot to the other and for a moment a small gap opens between his body and the door jamb. Years of Tai Chi training mean he catches something - a flicker in my eye perhaps - and moves easily to close the gap, before the intention to dash through it has fully formed in my mind.
A glance over my shoulder shows the window is closed and twenty feet above the ground anyway. There is no way out.
"We all know fruit is good for you," he continues. "We buy tonnes of the stuff every day. We stick it in our fruit bowls. We look at it. We think, 'I should eat one of those little buggers because I don't want heart attacks or strokes or hardening of the arteries or erectile dysfunction or herpes or ...."
"I don't think fruit stops you getting herpes," I say, but he isn't listening. I wonder if I can dig a tunnel and escape that way, but can see no shovels in the kitchen.
"See fruit is good for you," he goes on. "We all know that. But in a cold place like Scotland you don't feel like eating fruit. If your arse is frozen solid and your lips are chapped and blue, the last thing you want in your mouth is cold, wet stuff that tastes sour.
"So what happens?" he says and I try to jump in with a reply. "I'll tell you what happens," he continues without a pause. "Everyone in Scotland buys fruit every time we go into a supermarket. But we can't eat it because we're not sitting around in the sunshine. We're working our tits off to keep ourselves warm and get the economy out of the mess the fruit-eaters have got us into.
"So the fruit we've bought sits in fruit bowls for weeks, feeding the fucking fungi, while soft, warm southerners crack moronic jokes at our expense and live twenty years longer than we do, the bastards."
"Listen, I can't stand here talking to you all day," he says, stepping away from the door at last and gesturing with his thumb to the hallway.
"Have a banana and bugger off. I have work to do."