How we met: Thomasina Miers & Tristram Stuart

'I kept copious notes on Wahaca to give her – though I lost the lot in a UN compound in Nairobi'

Miers says: 'The amazing thing about Tristram is that he's fun, a delight to be around, but he really knows his stuff' (Carol Sachs)

Thomasina Miers, 37

After winning 'MasterChef' in 2005, Miers founded the Wahaca chain of Mexican street-food restaurants. She has also presented a number of TV shows, including 'Mexican Food Made Simple'. She lives in London with her husband and two children

We met at a party eight years ago – through one of his cousins, who was one of my best mates at university. He was fun and chatty and he told me how, as a teenager, he'd reared his own pigs, selling the produce to his friends' parents. He was then still living the "good life" now, in Sussex, growing vegetables and living off the land, which I was impressed by, because I'm into where food comes from: I've killed and butchered pigs, birds and fish; we shared the same wavelength.

In 2009, he asked me to get involved with his event Feeding the 5000 [where 5,000 members of the public are served meals from wasted fresh food], and I agreed. At Wahaca we recycle food waste to make compost, so it struck a chord with me. I ended up doing a cooking demo at the event at Trafalgar Square.

The amazing thing about Tristram is that he's fun, a delight to be around, but he really knows his stuff: he spent seven years writing a book about food waste [Waste: Uncovering the Global Food Scandal]. I feel lightweight in front of him: while I research recipes for a living, he takes on hard issues.

One afternoon we were having lunch at my restaurant and I said, "You must try our pork tacos." And he said, "I try not to eat pork, as it's not sustainable." I started bragging about what great husbandry we had – and he shot me down in flames. He said, "Well, it will still be fed grain from the other side of the world, which is destroying the Amazon."

I couldn't believe something so obvious as feeding our own catering-food waste to pigs could be banned. It's crazy, and I told him we should do something about it. So we started working on this campaign together, the Pig Idea [which saw thousands of pork lunches, made from pigs fed on waste, served to the public in Trafalgar Square earlier this month].

Some food activists seem to focus on how not to enjoy life; their approach feels dogmatic. But Tristram enjoys eating and he loves meat. We had a big feast together at Stepney City Farm recently: we had these incredible chefs such as Fergus Henderson and Bruno Loubet come and cook a mini piggy feast; it was a great afternoon.

We're quite different as people, in that I'm a London girl who likes to go out shopping and for dinner, while he's more of a country squire who lives off the land. Though he does also jet around Europe speaking to politicians.

He's just had his first baby, which I think is interesting for an environmentalist – though I like how it hasn't changed his lifestyle.

Tristram Stuart, 36

A food-waste campaigner, Stuart organises the Feeding the 5000 event in London's Trafalgar Square. He has also written an award-winning book on the subject, 'Waste: Uncovering the Global Fod Scandal'. He lives in Hackney, London, with his wife and daughter

I was briefly introduced to Thomasina at a party in London, in 2005, after she had won MasterChef. She is an old friend of my cousin's, so I'd heard a lot about her, and people had often said, "You would get on great with Tommi." I didn't actually watch MasterChef, though, as I don't have a TV – who has time to watch television?

I received a few invitations from her to go to various events but I didn't engage with her until I really needed a chef for my first Feeding the 5000 feast, in 2009. I was touched and delighted when she said yes: she was well known by then – and she'd started Wahaca – so I felt she brought a lot more legitimacy to the campaign than I did. I remember standing with her in a freezing-cold, empty, Trafalgar Square on the day of the event, Tommi brimming with enthusiasm, and I realised that this was someone I would get on with very well. Tommi did a cooking demo on the main stage; she explained how to use the whole carcass of a chicken. It was brilliant.

We didn't just pull off a fantastic event, we became friends. Though because of how we met, our conversations when we go out for lunch or see one another out, have always been about serious issues. Our friendship was truly secured, though, when she gave me the Wahaca Gold Card – I could bring up to three friends along to eat there for free. All I had to do was tell her what I thought. I've been a lot, and kept copious notes to give her, though recently I lost the lot in a UN compound in Nairobi. I don't know if she knows about that!

One afternoon we were sitting in her restaurant, having lunch, when we got on to the subject of the ethical pork on her menu. She said, "We have great sustainably reared, free-range, organic pork." And I said, "Yeah, but that's not good enough! They're still eating virgin crops that people could be eating, and it's reliant on 40 million tons of soy, which is driving deforestation in South America; we should be feeding pigs waste." That's when we came up with the Pig Idea campaign, to lift the ban on using catering waste to feed pigs.

About eight months ago we started rearing pigs for the feast down at Stepney City Farm, using food waste that you can feed pigs on: discarded grains from the local brewery, and wasted whey from a Peckham cheese-maker.

I remember going down to the farm with Tommi to give them their last meal, hand-feeding them Little Gem lettuces. It was raining and we kept getting pushed over into the boggy mud by these huge pigs: it was fun, but the last time that we would get to see the pigs; I think Tommi might have been more sentimental about that than me.

For more: feeding5k.org, thepigidea.org