For the past few months, Sir Peter Hall has been jetting all over the world, delivering lectures and attending specialist meetings from the US to Australia and China. "Actually, single-handedly, I've almost destroyed the planet," he jokes. "I've flown 50,000 miles in April and May alone, went to California for a conference, came back, went out to Australia, came back, went to Singapore, then over to Shanghai to give a lecture at a university centenary, then to Seville for a meeting, and Brussels last week."

A remarkably youthful 75-year-old, Hall shows no sign of letting up. He says he feels fine and somehow manages to fit in his "day jobs" in Britain - Bartlett professor of planning and regeneration at University College London, chairman of Blackpool's urban regeneration company, regular columnist in specialist magazines, prolific writing elsewhere, and with a rate of globetrotting that would make younger men tremble. "Actually, I'm sleeping very well," he volunteers in the splendid offices, near the Mall, of his beloved Town and Country Planning Association (TCPA), of which he is president and long-time activist.

As the foremost geographer and planner of his generation, Hall feels compelled to write about every place he visits with a journalistic skill - a keen eye, attention to detail, bound in an immensely readable style - that eludes most academics.

The fruits of his labours, closer to home, will be unveiled shortly in a new book, London Voices, London Lives - Tales from a Working Capital, to be published soon. Hall, who has written well over 30 books - including the masterly Cities in Civilisation (1998) - has charted the "extraordinary changes" in the capital over the last 50 years. The book's genesis lies in a project, undertaken with a team, that included 130 interviews for an Economic and Social Research Council-funded project. "They were fascinating when transcribed," he says, "but we only used a fraction of the material and, at the end of it, we said to ourselves: 'This is fascinating stuff. Shouldn't we make another book out of it?'"

Fascinating because of ordinary lives? "So ordinary, yes. It brings out the differences between one part of London and the other. We started out in Reading, because we thought this was a typical Thames Valley boom town. Then we jump over to Hounslow, which we call airport city, and is also a big area of Indian sub-continent settlement, mainly Gujurati from the 60s and 70s. Now many of them are saying: 'Oh, we don't like it here (now) because of the immigrants. We need to go to Surrey.'"

But it is Gants Hill, near Essex, that Hall finds "absolutely fascinating", as 1930s suburbia, which was very largely Jewish. "They came out from Whitechapel and now they are being replaced by people from the Indian sub-continent who have come from Whitechapel."

Born in Hampstead, north London, Hall went to live in Blackpool in 1940 when his father, a clerical officer in the pensions service, was dispersed to the seaside resort. Consequently, he is proud to call himself "an honorary Blackpudlian" and is deeply grateful for "an extraordinarily good education" in the town's grammar school.

He is now repaying his debt to the town as chairman of its urban regeneration company. Part of his crusade to reinvent the resort involved a campaign to bring a super casino to the seafront in an attempt to kickstart wider regeneration. But earlier this year, to the surprise of almost everyone, an independent planning panel said the super-casino should go to Manchester. Uproar ensued. Hall says the latest intelligence indicates that the government will "park" the plan, and instead allow 16 smaller casinos to go ahead.

Interviewing Hall is rather like attending a tutorial: endlessly informative, and amusing. His planning/ academic career took off with the publication of his book, London 2000, in 1963 while at Reading University as a young Fabian. "It was really about planning London at a time when planning was at the top of the public agenda in a way I think it has never been since."

He was invited by the government to join the South East Economic Planning Council. It was abolished in 1979 by Margaret Thatcher. "I wrote afterwards that the greatest irony was she shut it down because she thought it was not making any contribution, and we had three big agendas in our last years: one, that you would never develop London Docklands without an urban development corporation; two, that London's third airport should be at Stansted; and three, that the first national transport priority should be the M25 orbital motorway. So she shut us down rapidly to implement all three!"

As the TCPA celebrates the 60th anniversary of the Town and Country Planning Act, Hall is no starry-eyed sentimentalist longing for a return to the interventionist politics of post-war Britain. He says: "The act really assumed that the private sector wouldn't be very important any more, that most of the houses would be built by the public sector for the workers - a bit like a liberal communist country."

Now the world has changed and Hall's view is that it should be possible for planners to determine where development takes place, with the private sector delivering housing and new settlements. "We do know this is possible because we've been doing it very successfully in new towns such as Milton Keynes, where you had a very strong, positive planning thrust."

One of his regrets is that planning became such a pejorative term during the Thatcher governments that the discipline was ground down over 20 years to the extent that there is now a shortage of professionals. "Training plummeted and the profession became beleaguered, overloaded and overworked," he says.

His other regret is that the volume house builders have morphed into land speculation companies, holding back valuable, desperately-needed building land to boost balance sheets. His answer? "You have to have strictly [time] limited planning consents and take it [land] off them and give it to someone else to develop. I really do."

Career1992-present Professor of planning, University College London; 1989-92: professor, city and regional planning, University of California, Berkeley; 1968-89: professor of geography and dean of urban and regional studies, University of Reading; 1966: reader in geography, London School of Economics; 1957-60: assistant lecturer/lecturer, Birkbeck College, UCL.

Public life President, Town and Country Planning Association; chair, ReBlackpool URC; 1991-2004: special adviser, environment secretary of state.

Interests Reading, writing, exploring cities.

· London Voices, London Lives - Tales from a Working Capital, is published on July 10 by the Policy Press (hardback £65.00; paperback £24.99). To order a copy for £22.99 with free UK p&p, go to guardian.co.uk/bookshop or call 0870 836 0875

· Email your comments to society@guardian.co.uk. If you are writing a comment for publication, please mark clearly "for publication"