"There's widespread ignorance of the humble chip," he says, mounting the soapbox for perhaps the last time. "But this is a product that, compared to what the rest of the fast-food industry offers, is wonderfully nutritious and healthy.
"But being popular and nutritious, the potato is commonly harangued by the press. Potatoes are tremendous and people fail to appreciate the 'common' spud. There's nothing common about it: it is a fantastic vegetable and its true worth needs to be recognised."
Such fighting talk moves mountains. This year is the International Year of the Potato, designated by none other than the UN. Global potato production, meanwhile, has increased annually by 4.5 per cent over the past 10 years.
And closer to home, the BPC has scored stunning success even among sundry media cynics. The ongoing Potatoes for Schools campaign is set to reach 250,000 children this year and spur them and their teachers on to grow their own spuds.
Then there's National Chip Week, another ruse from Walker's team, which is egging on consumers with its "Love Chips!" slogan on Valentine's Day. What's needed is some high-class cachet, and if it doesn't come from TV celebrity Keith Chegwin, top chef Mark Hix is a safer bet. The chef at two of London's most famous restaurants, The Ivy and Le Caprice, has been roped into the campaign and is giving badly needed lustre to the potato.
Behind the marketing glitz, potato politics is in for some big changes with far-reaching implications.
All the levy groups are being merged into a hulking-great agricultural and horticultural development board, and the BPC is to become the Potato Council. But Walker is reluctant to talk about regime change or what it will mean on the potato patch.
"Now is a good time to go," he says. "The new set-up deserves new leadership. I'm reluctant to talk about a future in which I don't play a part, but the new composition of the board will include existing and past members and will be strong on talent."
And strength is paramount in the years to come, he insists: "The biggest challenges for the industry are sustainability and reducing our impact on the environment. If we can learn to grow more efficiently, we will use less land.
"Meanwhile, the impact of climate change will be enormous, if last year is anything to go by. The best potato land is often the most prone to flooding and this makes our industry a high-risk one. Good water and waste management will be crucial."
Walker has a powerful presence and the verbal skills to match. Last year his leadership qualities won him the British Potato Industry Award. Two years earlier he was expounding the virtues of the humble spud to the Queen after collecting an OBE.
These career highlights are as welcome for the bigger profile they bring to the potato industry as the allure they confer onto the man who has led that industry since the BPC was formed in spring 1997.
It now represents 3,000 growers, and Walker has the mindset of the "independent businessman" he boasts of being, and must be. Postholders with no political or ministerial affiliations lead the BPC for three days a week, at £50,000 or so a year.
Walker went to agricultural college before launching a successful career in the agrochemical sector. This saw him hold top jobs and chair the British Agrochemicals Association and other industry groups where well-formed opinions are a must.
"I have always had a clear vision of what I wanted the potato industry to look like. Growers, packers, merchants and marketers must work together because - although this is a relatively highly developed industry - there are tensions in the supply chain.
"If this job doesn't demand passion, it evokes passion. Some growers lost 70 per cent of their crop last year and the challenges that cause these problems mean you can't be half-hearted in the potato industry. You're either in it or you're not."
1960s: Studies agriculture at Writtle College, Essex
1970s: Joins chemical division of Shell and rises to commercial manager
1980s: Becomes managing director of agrochemical firm Cyanamid
1990s: Heads up BPC and British Agrochemicals Association
2000s: Awarded OBE for services to the potato industry and wins British Potato Industry Award
2008: Stands down as BPC chairman.