Bill Bryson is in a great mood. The man who has made a career out of being mischievously forthright about places as far afield as Arctic Norway, the Australian outback and even his hometown of Des Moines, Idaho, is coming to Oxford – and he has good things to say about it.

The author and journalist has not always been a great fan of the City of Dreaming Spires. Despite being in awe at the amount of history crammed into its streets, in his book Notes from a Small Island, he shared some forthright words about the “gross indifference and lamentable incompetence” with which our city is run.

That book was written as he left his adopted home in Yorkshire to return to the States. Now he is back – feeling very much at home down the A34 in Hampshire – and he appears to have mellowed in his opinion of the place.

“I’ve said many times that Oxford is the most improved city in Britain,” he tells me.

“It’s always been a great beauty, but in the 60s and 70s it went through a period of adopting brutalist architecture, leading to some not very attractive buildings in the city. And not just the university either.”

Though he adds: “Most of those buildings have either been torn down or improved, and there has been a big difference in the past 15 years, with some really great modern buildings together with the lovely old ones.”

He also waxes lyrical, perhaps surprisingly, about our park & ride system, saying: “It makes you feel noble when you use it. We have nothing like that in America.”

Bill, however, is not coming to town to talk about architecture, even less integrated public transport.

After a career which has seen him writing a string of travel books – from tramping the Appalachian Trail to exploring Kenya and the quirkier parts of Europe and the USA – and expounding on language and history, he is now expanding his interest in matters scientific.

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Having scored a best seller with his A Short History of Nearly Everything, he is turning his attentions far closer to home with a look at the human body, in the shape of new book The Body: A Guide for Occupants.

“I’ve lived in this body all these decades and have had no idea how it goes together and works,” he says. “It’s been looking after me all this time and I was quite interested to know how.

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“This is not me thinking, but learning and understanding the topic and putting down what I’ve learned. It seemed to me a natural sequence after A Short History of Nearly Everything.”

And it is that book which forms the basis for his new live show: Observations on Life and the Human Body, which comes to the New Theatre Oxford on Saturday.

He says: “We are infinitely more complex and wondrous, and often more mysterious, than I had ever suspected. There really is no story more amazing than the story of us.

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“But I have never done anything like this before. A whole show about a book. It’s much more fun than standing at a lectern reading. It’s terrifying; I’m not a performer, so let’s see how it goes.”

A self-declared Anglophile, Bill is a British citizen, has an OBE, is a Fellow of the Royal Academy, has 11 honorary doctorates and is a former Chancellor of Durham University. He is also a former president of the Campaign to Protect Rural England and an avid litter picker – showing, and shaming, us to keep our often country tidy.

But how did he first become so attached to this ‘small island’ – the place he began his writing career, first at the Bournemouth Evening Echo and then at The Times and Independent?

“When I left home in America, I planned to go hitch-hiking around Europe and go home to stumble into a job,” he says. “But then I met a girl and that changed everything.”

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That girl, Cynthia Billen, became his wife, played by Emma Thompson in the movie version of A Walk in the Woods (in which she was called Catherine). Bill was played, flatteringly, he admits, by Robert Redford.

“As I was falling for her, I was falling for Britain,” he says. “I wouldn’t have believed it.

“I’ve been really lucky and can’t believe how well everything turned out. But I am lucky to have had a happy marriage and kids and to have lived a life with no real crises.”

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So why has he turned away from travel writing? “I stumbled into travel writing but I’m not a good traveller,” he laughs. “I was just fascinated by the world I was travelling around. And there was pressure on me to do more travel books, and I enjoyed it.

“Being a travel writer is the biggest legal scam I have come across, though, because you get to go to wonderful places – places people save up for a long time just to go for two weeks – and you get to go for months and call it work!

“I do love it – and there are loads of places I’d love to go, but the best thing would be going to those places and not having to write about them. Writing's hard work!

"I’m looking forward to travelling to places with my wife – especially the places she hasn’t got to go to.”

His books contain countless hilarious encounters and comic situations. Does he ever, I ask, ever feel tempted to exaggerate?

“Everything I write about is based on something that has actually happened,” he says. “But I may say something for comic effect,” he laughs.

“If all I did was extremely literal, I wouldn’t have a book!”

Bill Bryson - Observations on Life and the Human Body is at the New Theatre Oxford, on Saturday. Tickets from