'I have a big problem,' says Baroness Susan Greenfield, perched on her black leather sofa in her Bond-style penthouse apartment. 'I love eating, but I hate cooking. I can hardly boil an egg.'

Greenfield has been dubbed 'neuroscience's answer to Emma Peel', and often unsettles fellow scientists with her taste for Armani miniskirts, her famous appearance in Hello!, and public admissions that - shock, horror - she reads Glamour magazine and would like a better bum, 'like Kylie's'. It seems that, despite her prestigious role as professor of pharmacology at Oxford university, her seat in the Lords, and her position as director of the Royal Institute, Greenfield's femininity and independence haunts her academic career.

The one thing that her critics will never be able to accuse her of being is a domestic goddess. 'I find it stressful. I'd much rather do what most people would call work - like write a book. So I've adopted a "can't cook, won't cook" attitude, and stuck to it.' Her aversion to cooking hasn't really proved to be a 'big problem'. After all, she happily lives on M&S meals and restaurant food, her fridge is stocked with Cristal champagne ('a present') and, if she feels like giving a dinner party, the only ingredient she needs is a telephone. Greenfield has the enviable capacity to do what many can only dream about: she can invite Rick Stein and Heston Blumenthal over to cook her Sunday lunch. And they accept.

This Sunday Rick Stein is happy to whip up a fish starter, her PA Vivienne will prepare the main, while Heston has brought pudding. 'A chocolate cake with a twist,' he says with a cheeky smile. Susan has even called on a colleague, Marcus, who has access to a university wine cellar and arrives bearing bottles worth up to £100 a bottle. Greenfield has been friends with Rick's brother John, a fellow neuroscientist at Oxford, for 30 years. Also attending is her neighbour Caroline Lloyd-Davis, John Stein's wife Clare, Heston's wife Zanna, and Jonathan Christie, a travel agent and old friend.

Both Rick and Heston have done research at the Royal Institute and were keen to share an informal Sunday lunch together. 'I've only eaten at Heston's place once,' says Stein, cutting slivers of tuna from the vast deep pink slab he has brought from his restaurant in Padstow. 'I just thought the whole experience at the Fat Duck was funny. It doesn't take itself too seriously. I think there is room for traditional food that is intellectually challenging. Though, personally, I prefer sausage and mash.'

Stein is wary of the interest in the new breed of science-based haute cuisine, led by Heston Blumenthal and Spanish chef Ferran Adrià. 'I find the huge enthusiasm of journalists for this type of wacky "molecular gastronomy" slightly sickening. Basically it's just a good story.' He does, however, recognise its economic potential: 'First and foremost this business is about making money out of restaurants, because otherwise you don't survive. Any way of keeping customers coming back is worth doing. It's just amazing to me how this new scientific cooking has caught on. I wouldn't be at all surprised if, at the beginning, Heston wasn't just doing it as a bit of a private enthusiasm and then suddenly found himself in the centre of international acclaim.'

Blumenthal, however, is captivated by what science can bring to our plates and thinks the enjoyment of food can be enhanced by knowing the processes behind the dish. He has issues with the 'molecular gastronomy' label, because, he says, 'it gives people the wrong idea and scares them away from finding out more. My kitchen is not a lab, it's a kitchen that has some new cooking utensils in it.'

The Cristal flows and Susan's guests gather on the balcony. Just like the flat, it's sparsely furnished and keeps to the jet-black theme that runs through her open-plan living room and kitchen. Susan has lived here since 2003, after her highly publicised divorce from fellow Oxford professor Peter Atkins. 'I wanted something fun,' she explains, each word shooting out like machine-gun fire through a fixed smile. 'I spend half my time at the Royal Institute in London, which is a Grade I listed building. This is a counterpoint to that. It's wacky, and slightly frivolous.'

Enter the flat and you find yourself in a hall covered in blue sky and clouds. The result is a heavenly vision that disappears once you've walked upstairs into an expanse of black furniture, silver wallpaper and flashes of red. A contestant on Through the Keyhole would be stunned to learn that this wasn't the flat of a 30-something bachelor. A photograph of leggy chorus girls hangs on the wall; the dancer on the far left is Greenfield's mother. 'She was one of the Sherman Fisher Girls,' she says proudly.

Greenfield seems to thrive on extremes and breaking expectation. She wasn't put off when leading scientists threatened to resign from the Royal Society if she was elected to its ranks. They accused her of courting the camera lens, rather than concentrating on research, but Greenfield sees great importance in bringing science to the public and is determined not to stop going to fancy hairdressers or eyeing up shoes (she has a soft spot for platform boots), just so that people will take her 150 published papers seriously.

Her latest book, Tomorrow's People, looks at how technology will shape our future, and sees the future of food as being, 'square - so it would stack well and won't drip down your shirt.' She also talks about an increase in the production of 'nutraceuticals': dishes packed with nutrients. The book predicts that the fight against GM food will be lost since manufacturers will find a way of enhancing the pleasing elements of, for instance, a strawberry, making the natural alternative taste bland in comparison.

She has been called pro-GM but is actually undecided. 'I'm pro an open mind and I'm pro-science,' she states, raising her voice a little above the Eagles track that's playing. 'If I'm faced with GM versus non-GM in a shop, I'll reach for whatever is the best value. I think it's ridiculous when people say they won't eat GM foods until someone proves it's safe but then start ringing someone on their mobile.'

In Greenfield's vision of the future, ovens would talk and fast food would be as reviled as cigarettes . 'I thought it was fascinating when the teachers on Jamie Oliver's recent programme reported that the children were more calm and better at learning after they were given a healthy diet. That is surely a wake-up call .' Greenfield hopes to widen her research to look at neuroscience in education, and knows that any study of how children are learning would do well to include research into their diet. No doubt she can consult John Stein during this project. John has no interest in cooking, 'I don't do cooking, my brother doesn't do neuroscience,' he announces.

However, he does take a scientific interest in food and how it can shape behaviour. His junior colleague, Dr Alex Richardson, did the recent highly publicised research into the health benefits of omega-3 oil found in fish. 'We were not in the least surprised by the results. We had done lots of studies showing that omega-3 fish oil supplements can help children learn to read.

Another study gave supplements of fish oil and vitamins to young offenders. They found that it reduced the rate of reoffending by a third, which is amazing. It's a shame that nowadays people eat very little fish.'

Luckily, his brother is 'Mr Fish', and spends a good deal of his time promoting it. Stein's first course of raw tuna fish starter marinated with passion fruit and green chilli goes perfectly with the Tower Chardonnay he's bought (from the winery he co-owns in South Australia). It's a new, Australian-influenced recipe. 'I'm always looking for little fresh-tasting fish starters and I think a . first course should be really light.'

Everyone loves it. Vivienne serves out her contribution, a main course of pigeon with lime and coriander crème fraîche and lentils with wild garlic. She doesn't seem fazed at being sandwiched between two of the world's greatest chefs, and she's no need to because it's delicious. However, what everyone is really waiting for is Heston's 'twist' to what appears to be a classic chocolate cake. 'Oh,' says John Stein's wife, Clare, a little startled. 'Spacedust?' says a bewildered Rick Stein.

Heston has added popping candy to the base and inside is a layer of leather-infused Aero. 'Chocolate has the same compounds as leather, you see. So I thought I'd bring out the leather element to the chocolate. Whisky has the same compound too,' he explains. It's the first time he has made the cake and it is eaten with sudden explosions of laughter. For Heston this is how it should be. 'I thought it was great when Rick Stein said he found my food funny.

One of the nicest things you can do is spend time round a dinner table. We work the longest hours in Europe, and so you need to be able to laugh.' For Blumenthal, three Michelin stars and his recent accolade as the world's best chef, means the pressure is on every day. 'It's like being patted on the back and kneed in the groin,' he says. His restaurant is booked for months in advance and his 20 phone lines are so blocked with incoming calls wanting reservations that it's impossible to make internal calls. Susan, who has never been to the Fat Duck, listens, and smiles a request, 'I'd love to go.'

Then she tells Heston about her first and last venture into cooking. 'I was a student and was having people round. I saw this pig's head in the market which was only about 20p and thought "that's cheap". I bought it, but hadn't a clue how to cook it. The head filled my tiny oven and I didn't know how ovens worked so I just turned it up high. It went gold and, after having put an apple in the mouth it looked perfect, like something from a medieval feast. I was quite proud until someone cut into it and fat and raw meat spurted all over us. I hadn't cleaned it properly - there was still wax in the ears.' Heston smiles and responds, 'Yes, you have to get the ear wax out'. He's looking ponderous, as if Susan has given him ideas. You never know, perhaps with the appliance of science, a pig's ear wax starter might be delicious.

Rick Stein's marinated tuna with passion fruit, lime and coriander
Serves 4

1 3cm thick piece of tuna loin fillet, weighing about 400g 2 small ripe and wrinkly passion fruits (each weighing about 35g)
1 tbs lime juice 3 tbs sunflower oil
1 medium-hot green chilli, seeded and finely chopped
1 tsp caster sugar
11/2 tbs coriander, finely chopped salt and black pepper

Put the tuna loin onto a board and slice into very thin slices. Lay the slices close together, over the base of four 25cm plates. Cover each one with cling film and set aside in the fridge for at least one hour or until you are ready to serve. To make the dressing, scoop the passion fruit pulp into a sieve over a bowl to extract the juice (it should be about 1 tbs). Stir in the remaining ingredients. Spoon the dressing over the fish and leave for 10 minutes before serving.

· Rick Stein's French Odyssey begins in August on BBC2. Susan Greenfield's Tomorrow's People: How 21st-Century Technology Is Changing the Way We Think and Feel (£7.99, Penguin) is out now.