Sheila Dillon offers me a choice when I suggest that we meet over lunch. There is an interesting restaurant in the middle of London that has a wormery to dispose of its leftovers. Or one which has its own farm in Northumberland which provides all the beef and lamb it serves. Food, for the presenter of the BBC's The Food Programme, is never anything as simple as a little of what you fancy.
Nor is any detail too small to warrant scrutiny, which is why the award-winning programme, originally commissioned for a six-week run, tomorrow celebrates its 30th anniversary. Dillon passed the butter. A rare treat, I ventured, for those of us who don't have it at home.
"What do you have?" she asked, and when I told her the name of the spread, she arched her eyebrow. "Have you been listening to the programmes we've been doing about omega-6 in margarines? Some scientists think that in the wrong balance with Omega-3 it's linked to heart attacks, strokes and depression." Butter is better, so long as you stick to small amounts. Which she does with her herb and carrot bread.
Food, for Dillon, is a mixture of pleasure and politics. "It's about making connections," she says, "and linking the food on our plates to the world around us." Under her guidance The Food Programme, where she has worked for two decades, first as its producer and now as its presenter, is a culinary cornucopia which mixes campaigning and celebration of food in equal measure.
Its programmes heighten the sensory appreciation of garlic, eel, champagne, goose, chocolate, almonds and rhubarb. But it also turns an investigatory spotlight on to the plight of the honeybee, Fairtrade coffee, the state of school meals, the closure of small abattoirs, sustainable fishing and our changing relationship with meat as climate change impacts on the world's food production.
The recipe goes down well with 1.7 million Radio 4 listeners each Sunday lunchtime and attracts a firmament of awards and prizes from the broadcasting world. Last year it even earned Dillon an honorary doctorate from City University for work that "has changed the way in which we think about food".
It's an accolade she cherishes almost as much as the condemnation of the louche restaurant reviewer A A Gill, who once called her a "Stalinist" by comparison with her predecessor, Derek Cooper, who launched the programme in 1979 and presented it for 23 years. The contrast was illusory; Dillon had previously been Cooper's producer for 17 years and had played a key role in shaping the programme's success.
Over those years The Food Programme has charted what she calls "three decades of unprecedented and dramatic change". Its narrative has been the globalisation of our food system as post-war governments pursued a policy of cheap food and scientists sought an agrochemical solution to every farming problem.
"It has been characterised by a massive shift in power from the manufacturer to the supermarket," she says, "leading to a world where recently thousands of tons of Cornish cauliflowers, which because of the weather had turned out slightly smaller and a little creamier looking than supermarket standards permitted, were ploughed back into the earth."
But it has also been a time when the small man and woman struck back. Sunday's 30th-anniversary programme celebrates one of the most heartening changes of the past three decades – the rebirth of British farmhouse cheeses, a once-fading craft that is now undergoing a glorious resurrection.
Dillon has not just reported on that, she has been crucial in nurturing it. It was her programme, too, that did the first report on a farmers' market, in Bath. "The next day we had 41 local authorities on the phone asking how they could start one," she recounts.
As our lunch arrives – braised dishes of beef and neck of lamb – she recalls how in 1987 the programme set the agenda on BSE long before the newspapers woke up to the problem. "I went to the lab in Edinburgh working on scrapie [the degenerative disease in sheep]. I asked one researcher if he had changed his own diet, and he disclosed that he had stopped eating burgers, pies and sausages. It was then I started to wonder about the government assurances that diseases like this could not be transmitted to humans."
Through it all the programme has struck a note which is authoritative, informed, sceptical and always seems on the listener's side. It has balance. Though it warned of BSE it adjudged that there was unjustified panic over listeria fed by a Government overreaction to a dairy industry dominated by big companies which didn't understand that craft cheese-makers did not need to pasteurise because they knew the source of all their milk.
Dillon strikes a middle way, too, on GM foods. "Opposition has become ideological because of the way GM was developed as an instrument of commercial control rather than as something for the benefit of wider humanity. Now if we could take the gene for short-chain omega 3 from algae and put it into oilseed rape..." The virtue, like the devil, will be in the detail. "It all needs scrutinising."
In a world where programmes about food usually mean celebrity chefs, drooling foodie porn and reality dinner parties, The Food Programme stands out as a bastion of intelligence and integrity. It will be needed more than ever in the next 30 years.
"Our present food system is dependent on using vast amounts of diminishing water and cheap oil for energy," she says. "The world will have to face the question of how to produce food sustainably while also feeding a growing population. Much-mocked middle-class ideas about our eating stuff only when it is in season will become a necessity for everyone."
Our coffee arrives. "A cappuccino costs around £2 in the UK. But the Ethiopian farmer who produced the beans – generally agreed to be the finest on the planet – will get perhaps 5p a kilo. The arithmetic isn't difficult," she says. "This is one of the reasons Ethiopian farmers and their families are going hungry, need food aid and are getting out of coffee growing. Understand food and you're a long way on the road to understanding the way the world works."