When I go to see Conran in his Bermondsey headquarters - a Michael Hopkins building tucked away behind his celebrated Design Museum, and handy for the slew of Conran restaurants and shops along the river that he calls his “Gastrodome” - it’s a typical English summer’s day. Thunder, lightning, sheets of rain, darkness at noon. Conran sits with his window wide open to all this, at his big Conran table. Various representations of Mr. Bibendum, the Michelin Man who gave his name to the first of his new-generation restaurants in 1987, are scattered around the glass-walled office. Visitors like me sit in an Eileen Gray “Bibendum” chair. The well-padded Conran does not like to imagine a life where good food is not central. “There are apartments in New York that are designed with no kitchens,” he sighs. “Of course, it’s anathema to me.”

Conran’s studiedly relaxed demeanour, as the storm crashes around outside, conceals a daunting work rate. He has been hard at it for 50 years, ever since he got his first and only salaried job, helping architect Denis Lennon at the 1951 Festival of Britain. His worst time personally came in the 1980s as chairman of the huge and unwieldy Storehouse Group. This included BhS and Mothercare as well as Habitat, Heals, the Conran Shops and much else besides. It was extraordinarily ambitious and it was, he freely admits, a mistake. He never managed to persuade his BhS colleagues to buy into his personal design revolution. And he had to fend off successive takeover bids.

“ I remember sitting in meetings with merchant bankers, thinking - this is not what I want to do with my life,” he says. So he staged a strategic withdrawal, lost Habitat, bought back the Conran Shops, and re-invented himself as a hugely successful, even Michelin-starred, restaurateur. And he never stopped designing. His “Benchmark” company, based at his Berkshire estate, now employs some 40 people. There he designs and makes furniture for various clients including his own shops. It’s possible, he says, for him to do a sketch design on a Monday and have a complete prototype by Friday.

I tell him how I bought a couple of his “Le Coq” chairs recently - as designed for, and named after, his City rooftop restaurant Le Coq D’Argent - but that various friends are convinced they are 1950s relics. He pouts. “I suppose I’m a bit of a 1950s relic myself,” he responds, half-pleased, half appalled.

Terence wants to run Habitat again, even now, even at 70. He means it. “I miss Habitat. I miss that scale of operation”. The far smaller, more upmarket Conran Shop operation cannot compete on that level. So he watches Habitat closely - is an old friend of Ingvar Kamprad of Ikea, the Swedish chain that now owns it. He makes suggestions. He admires Tom Dixon and the other younger-generation British designers now in charge of the Habitat legacy. But Conran is very aware that most people still think he runs the shop, and sees no reason why he shouldn’t. “I think Tom and his team are doing an excellent job on the design side. But I just feel the lack of someone who really understands retailing in the place.”

He has bad memories of the 1980s for reasons other than the Storehouse imbroglio. It was the retro, Laura Ashley decade when his brand of indulgent modernism went out of fashion and his market researchers were telling his shop buyers to buy things that he, Conran, did not like. Since when, it’s all come around and Conran-style modern living is quite the thing again. Except, as he points out, in the huge mass-market housing estates around the country, where cod-historicism reigns unchecked. “I can’t believe the way domestic housing is so left behind in this country,” he says, “I feel so strongly about this. There must be a revolution in housebuilding. God knows how it can be made to happen.”

Conran describes his younger self in the 1950s as being the archetypal Angry Young Man. It’s clear that some of that anger still lurks beneath his well-upholstered, blue-shirted, cigar-puffing exterior. But maybe it’s anger at an opportunity missed. Maybe he should have led that housebuilding revolution instead of getting bogged down in ultimately fruitless mega-retailing. He won’t retire - he says he wants to die with an unfinished project. But not even Sir Terence Orby Conran can do everything.

“Q&A: a Sort of Autobiography” by Sir Terence Conran is published by HarperCollins on October 1.