Shocking news. The chef at Tom's Place, the 'green' fish-and-chip shop soon to be opened by the Michelin-starred chef, Tom Aikens, is French. This is worrying. The French, in my experience, don't really get batter. Tempura - the light stuff beloved of the Japanese - they understand. A zucchini flower kissed with flour, water and, at a push, egg: what's not to like? But British batter, crusty as old shoe leather, brown as syrup, and severely doused in malt vinegar? Non merci.

Aikens's identical twin, Robert, who is also a chef and who has overseen the menu at Tom's Place, looks at my disbelieving face with something approaching pity. 'We interviewed four chefs for the job,' he says. 'Three of them British, and Yves Giraud, who is French. We had a cook-off, and Yves' batter was the best. Really delicious. So he got it.' What about les frites? The French can be a bit prissy about chips, but in a chippy-type situation, we like them fat and soft as slugs. 'There will be a choice,' he says. 'Customers will be able to have chips cooked in rapeseed oil, or in beef fat.' He doesn't comment on size, but I've read elsewhere that the Tom's Place chips are to be neatly regimented, so as to avoid the tiny crisp ones I like to pick at even once I feel absolutely stuffed. Condiments? 'Yes, indeed [sounding ever-so-slightly weary]. On the table.'

It's important to get this stuff out of the way, I think. Tom's Place - in spite of its Chelsea address, and the fact that fans of Aikens' other establishments include high rollers such as Frank Lampard - is going to have enough of a job shifting customer perceptions as it is, without also having to persuade them of the essential rightness of the dishes on its menu. At Tom's Place, a piece of cod will cost £12, chips not included; pollock will set you back £11.50, breaded scampi £20. As for haddock, it will rarely be available at all. Instead, customers will be able to choose from such unfamiliar delights as grey and red gurnard, and megrim sole fillets. Will these prices come as a shock? Not, perhaps, to the premiership footballers among us. But many will look at the restaurant's (recycled) plastic tables and chairs and its cardboard (ditto) takeaway boxes, and think: Rip-off City. Because, for all that the cost of fish has gone up in recent years, we're still used to paying a fiver, or less, for fish and chips: a sum that reflects not the plenty of our seas (our waters have not been truly bountiful for decades), nor the unfashionability of fish (eating fish is hip: just ask any supermodel of your acquaintance), but the many and monstrous industrial ways it is caught and brought to our tables.

Tom Aikens is determined to make people realise this, and while he hopes that customers will enjoy the dishes at his chippy - also available will be bowl food like moules marinière - he is perfectly happy to admit that he also sees it as an educational tool. Over the past year, Aikens, who left school with only a pair of CSEs to his name, has spent every spare minute educating himself about fish; the more he learns, the more outraged he becomes. 'We've taken the piss dramatically with what we've been taking out of the sea,' he says. At the heart of his disgust is over-fishing: a ruthless habit that means that species like haddock and halibut are now so scarce, they cannot be eaten with a clear conscience. But it's not just the fishermen and the food giants they work for who are to blame for this. 'The press has not always been fair to fishermen. We should never have given away our fishing rights in the 1970s. Iceland has a 200-mile exclusion zone around its coast. Why can't we do that?' As for the EU quota system, he regards it as Kafkaesque: designed to protect vulnerable species, it means that fishermen who catch illegal fish by accident must throw them back even if they're already dead (since it was introduced in 1983, fish numbers have actually gone down). Aikens believes that we now find ourselves at a turning point, one he likens to the move back to more traditional farming methods that followed the BSE crisis. As Charles Clover puts it in his devastating critique of overfishing, The End of the Line, the true price of fish isn't written on any menu: unless things change drastically, we are nearing the end for global fish stocks. Anyone who thinks this is just scaremongering should remember the Mediterranean, now as barren as a swimming pool.

The fish at Tom's Place will be mostly line-caught, because it is the nets of vast trawlers that have put stocks in such peril (to visualise the devastating effect a trawler can have, Clover suggests that you picture a mile of net, a huge metal roller attached to its leading edge, strung between 'two immense all-terrain vehicles and dragged at speed across the plains of Africa'; not a nice image, is it?). It will also come from sustainable, Marine Stewardship Council-approved sources. He is using small, family boats in Newlyn, Plymouth, Hastings, Lowestoft and Peterhead, owned by fishermen with pride in what they do, expertise and morals. If a customer wants to know more, their questions will be answered: 'We have produced a booklet for the staff about our suppliers, and it's about an inch thick.' Will he able to persuade people to pay these prices? 'I think so,' he says, carefully. 'It's a case of people realising what is going on. For some of these companies, it's cheaper to ship whole, frozen fish to China, have it prepped up and breaded there, and then ship it back here to sell. What people are getting away with is disgusting.' As for persuading people to eat fish other than haddock and cod, he thinks taste alone will do it. 'Pouting, sprats, coley. These were the fish people used to feed to their cats. Gurnard, megrim, sole. These were the fish that were thrown over the side because no one wanted them. But they're lovely. Pollock has the same texture as cod, but it's creamier.'

Aikens is not the most likely eco warrior I have ever met. He currently has two restaurants: Tom's Kitchen, which serves casseroles and pies to people whose designer bags are nearly as big as their SUVs, and Tom Aikens, which has a Michelin star and is about as grown-up as a restaurant can be (people - I find they're men, mostly - talk of his braised pig's head with pork belly, stuffed trotter and celeriac lasagne the way Brian Sewell talks about Poussin, which is to say reverentially, and with their eyes half-closed). Aikens has, then, a lot on his plate - and, Michelin stars being what they are, is required to spend quite a lot of his time faffing about with sauces and generally questing for perfection. What I'm trying to say is: most chefs in his mould care more about how food looks and tastes on the plate than where it comes from, and leave all that stuff to their reassuringly expensive suppliers. I meet him at Tom's Kitchen (his brother keeps me amused until he arrives hot from lunch service at Tom Aikens) and even once he's in front of me, I can't imagine him marching on the Department of Environment, Food and Rural Affairs, placard in hand. He just seems so very west London. His businesses are all terribly Chelsea (Kate Middleton celebrated her birthday at Tom Aikens), and his new wife, Amber Nuttall, is the daughter of Miranda Quarry, an ex-Mrs Peter Sellers who is now married to the Earl of Stockton, heir to the Macmillan fortune. In his body warmer and dark jeans, he looks - and sounds - like the kind of man who'd take more interest in the top speed of his car than in the secret life of spider crabs.

But this is unfair. He cares deeply. His late father-in-law, Sir Nicholas Nuttall, first got him into in all this (Nuttall started a marine-conservation foundation in the Bahamas), and now the obsession with detail that helped him to become the youngest British chef ever to win two Michelin stars - at Pied à Terre - means that he cannot let it lie. He is absolutely serious, to the degree that, last year, he arranged to meet the fishermen of Newlyn while he was still on honeymoon.

'I absolutely hated school,' he says. 'When you go into catering, everyone assumes that you're dim. Now I have this real bug of learning, trying to get as much information into my brain as possible. People in restaurants talk about concepts, but they're only fashionable for about 40 seconds. I see this as having lasting meaning. Tom's Place is the beginning of something. Who knows where it goes next. I'm thinking about setting up my own foundation.' In March, he'll meet MPs to lobby them about these issues. I wish him luck. Given the political inertia on this up to now - as Charles Clover notes, fish don't vote; politicians have been ignoring the warnings of scientists about overfishing since the 1940s - he will need it.

Aikens was about 12 when he got into cooking. He was born in Norwich in 1970; his father and grandfather were in the wine trade. 'My dad used to take us to the vineyards in France to meet his suppliers, and my mum was a great cook, and it grew from there. I didn't respond to school; my teachers wrote me off as a waste of space. Even when Rob and I applied to catering college, well, he did a good interview, and I did a shit one. On the course, one of the teachers said: "You'd better keep your nose clean, or you'll be out. The only reason you're here is because of your brother." That was when I thought: fuck you. I'll show you. Twins are quite competitive. I told myself that, if I didn't made it by the time I was 26, I would have failed.' After college, he worked first at Pierre Koffman's La Tante Claire, then at Pied à Terre, under Richard Neat, and finally under Joël Robuchon, in Paris. In 1996, he returned to Pied à Terre as head chef where - aged 26 - he hung on to the two Michelin stars held by his predecessor. In 1999, however, he was sacked, after allegedly 'branding' a trainee chef with a hot knife.

The pressure, he admits now, really got to him. 'I was an idiotic lunatic in the kitchen. I was a nobody, so no one wanted to work for me, and there were three or four of us doing 20-hour days. I pretty much went round the twist. The adrenaline keeps you going. You think you're invincible. But I was very shy. I bottled things up until they all came out in one hit.' After he lost his job, he spent four months thinking: 'What the fuck have I done? I've ruined my career and probably a couple of other people's, too.' Then, in arrears on his mortgage, he asked Pierre Koffman for work. His old boss duly obliged, but by this point, his debts were too big. A friend told him that private catering was lucrative, so he gave his name to an agency, and within two days, he was working for the Bamford family, the extremely rich owners of JCB. Carole Bamford was in the process of setting up her business, Daylesford Organics, so, as well as cooking her dinner parties, he joined the team on her Gloucestershire farm. 'She's an amazing woman,' he says. 'She could just sit back and enjoy life, but she has a dream.'

For his own part, he could have stayed with Carole: flat, car, pay cheque at the end of the month. 'But it wasn't what I wanted. I craved the adrenaline of a restaurant. I was cheating myself.' His first wife, Laura Vanninen, began to look for a site and, in 2003, Tom Aikens was born. 'It was exciting, but I thought: you must be fucking mad, going back to those hours, to that shit. I had a bit of a breakdown. I doubted myself. Had a wobbly.' Feeling that everyone was watching, he again worked insanely hard; this time, the casualty was his marriage. 'Two people, working so hard [Laura did front of house], then going home together. It ended the year after we opened. It was very sad.' Amber is a former chef; can she cope with his work ethic? 'She's very patient. But I try to take the occasional evening off to spend time with her. Also, I'm a bit calmer myself. If a piece of meat is overcooked or over-seasoned, it's not the end of the world. Put another bit on.' But he'd still like to win a second star at Tom Aikens? 'Oh, yes.'

For now, though, the big excitement is the chippy. It's a good and a brave idea - the sheer logistics of getting fish to London from so many different boats, all of which land at different hours of the day, would put most people off before they'd even started - and I'm relieved to see that, for all the ostensible ponciness, we will still be able to buy both a chip buttie (£3.50 - eek!) and mushy peas (£2.50; let us pray that M Giraud doesn't do anything stupid, like adding mint). I just hope they will put Tizer on the drinks menu. Knowing what I do, I'd be happy to pay £12 for a piece of battered cod, Yorkshire roots or no. But I wouldn't be willing to eat it without a can of Tizer in my hand, not even if it died with a smile on its face.

· Tom Aikens on sustainable fish on our food blog

· Tom's Place opens shortly at 1 Cale Street, London SW3 (020 7351 1806)