“You know,” says Professor Raymond Tallis, gloriously topped with a straw fedora as he poses for pictures, “Kirsty Young said I was her favourite Desert Island Discs guest. You see. I'm the thinking woman's crumpet.” It's said with a laugh, but there's an unmistakable trace of pride.

Who can blame the self-deprecating doctor, philosopher, poet and author for being a wee bit pleased? He could, if he wanted to, lay claim to being one of our foremost thinkers on medicine, old age and the meaning of life generally. He's been a key adviser on health policy, headed a revolution in stroke care in his native Manchester, been lauded for his research in geriatrics, and written dozens of books on everything from neurological rehabilitation to the philosophy of consciousness.

But he's happier joshing that he's the pin-up of dishy radio presenters. It's his brain they go for. His latest book, Hunger The Art of Living, published this month, is a philosophical look at human hunger in its broadest sense our hunger for things, pleasure, sex and kicks, as well as food. Remarkably, it's the third book he's had published since 2006, when he retired from medicine to reinvent himself as a full-time author and thinker at the age of 59 and three quarters.

We're surrounded, appropriately enough, by leather-bound books in one of Tallis's favourite places his club, the Athenaeum, the haunt of Dickens, Humphrey Davy and 52 Nobel prize winners. He's relentlessly witty and learned as we talk about his life and beliefs, and why he and everyone else has reasons to be cheerful about getting older.

Retirement came as a shock

But reinventing himself after his retirement from the post of Professor of Geriatric Medicine at the University of Manchester has been unexpectedly difficult, he admits. There was a long period of depression. “I was completely taken by surprise how worthless I felt,” he says. “Suddenly I had the lost the thing which I valued myself for, but hadn't realised it, which was being directly useful. It wasn't about no longer being important or missing the theatre of medicine - because I'd actually found the unrelenting seriousness of that more and more difficult to bear as the years went on. It was a sense that what one was doing was less directly important. That made me realise the extent to which I had become a doctor. It's taken me two years to get over that. But I'm now no longer an ex doc. I'm an ex ex doc.”

There's always been an engaging streak of the showman in Tallis, 61, which partly accounts for his popularity on the radio and in public debates.

He says he likes hats (he also has a red felt fedora) not only to hide his lack of hair but to help make the case that he is not a boring old fart. His pink shirts, curled moustache and hurried Oxford-English (he was born in Liverpool and lives in Stockport) evoke the brilliant British eccentric as much as his learned allusions in every sentence (“As Pascal said ...”). But these are backed by an astonishing work rate and intellectual curiosity. He tells me, in passing, that he's just “ditched” 22 million words of his lifework about human consciousness, and is starting again. “It was becoming an incubus.” And through his career, he's made deeply serious arguments in support of medicine and scientific principles, and against the “pseudo science” that human beings are so easily seduced by. That means little patience for complementary medicine.

Or for popular fields such as evolutionary psychology, which propose that the evolutionary principles of survival that shaped animals also shaped human brains, behaviour and perceptions.“I have huge respect for our cat, but I don't think its job description in any way matches mine,” he says. He's also a fierce defender of doctors in the face of increasing media focus on their shortcomings and omissions, most vehemently expressed in his 2004 book Hippocratic Oaths: Medicine And Its Discontents. “I get cross because I think the life of a doctor is a difficult one,” he says. “We are getting more and more dissatisfied patients, paradoxically when the medicine is delivering more and more, better and better.”

Those advances mean we are all living longer. As a former geriatrician, you might expect Tallis to be pessimistic about the effects of age. But despite witnessing older people go through “utterly meaningless and unbearable suffering” as they have approached death (he has latterly come to support medically assisted dying) Tallis is optimistic about ageing. His own mother is still around at the age of 94.

“I have no problem about getting older,” he says. “There's no inevitability that a long life will be associated with a lot of ill-health at the end - in fact we're all staying healthier longer. And I don't think there's any intrinsic limit to what older people are capable of intellectually, because a lot of the diminutions associated with age are actually due to illness, such as cardiac failure and Alzheimer's rather than age itself.

“What gets me annoyed is talk about the‘demographic timebomb', and the assumption that we can't afford a lot of older people even if they're in good nick. But older people have an enormous amount to contribute either as a part of the workforce or generating ideas for society.”

The potentially long period of good health after careers have unfolded and children have left home presents, Tallis says, “an unwritten script” to be filled in.

“This is where human beings have a unique capacity to make themselves up. It doesn't necessarily mean endless easyJet weekends. It could mean something more profound than that. As T. S. Eliot said, old men ought to be explorers.”

It's typically upbeat, from a man with an almost spiritual belief that there is more to Man than an accumulation of molecules, that the human mind has no bounds, and that we are unique among all beasts because of our self-awareness. But that brings with it problems: hence his new book.

“Our hungers are one of the most obvious manifestations of our self-awareness,” he says.“We consume more because what we consume disappoints us, and I think once we identify our own hungers and the reason for them, we can find ways of managing zero growth, and downsizing individually and collectively. The best way to do that is to relish and enjoy what we already have.”

Tallis's mission to search for meanings as well as molecules goes back to his youth. He was one of five children to an “upright but fierce” father who came from a poverty-stricken background and whose own father was an alcoholic. He set up a building contractor firm, and managed to put all five children through a private schooling. Tallis's greatest inspiration came in his teens, in the form of a biology teacher who opened his eyes to the fascination of biochemistry.

But as he approached his 20s, he found a materialist biochemical view of the world - which didn't allow for higher emotions or free will - increasingly bleak. “Believing we were simply organisms designed to function and survive made me very miserable. I guess in many ways I've been arguing with my 15-year-old self over the past 45 years.”

Reading philosophy in his spare time provided an antidote to meaninglessness. And through medical training at Oxford and then London, through his years as a champion of geriatric care, Tallis has combined a working day focusing on the physical with early mornings and late nights turning to the metaphysical.

He's been married to Terry, a social worker, for 37 years, and says he's eternally grateful to her for taking the burden of childcare as he toiled. Neither of their two sons, in their twenties, has gone into medicine. “They've seen what it's like.”

For all his initial doubts, Tallis too is glad to have left medicine behind: new management regimes where Whitehall rather than doctors sets priorities, continual pressures to do more and get more right, and, most of all, the sheer burden of life-and-death decisions. Medicine has taken its emotional toll. “You were never sure if you'd got some of the decisions right,” he says. “As I look at it, an ethical decision is one where you feel uneasy whatever you decide. There's no ethical decision that will stand up to the court of conscience that meets at 3am when you get up for a slash.”

He worries about drinking too much

We talk about his own health, and he says he has mild hypertension, mild raised cholesterol, and he takes tablets for both. He worries about drinking too much (he listed Stella Artois as one of his recreations in Who's Who. “I do not keep within the limits, and as someone who's looked after people with strokes, I know what's at stake and it isn't a purely theoretical risk.”

So is it disability rather than death he fears most? “Definitely. I fear most not being able to speak, write or think. That would be my definition of Hell. As for death, I have no clear idea what's after it. Probably there's nothing, in which case there's nothing to fear. Except I'd like the sort of thing we're doing at the moment to go on for ever please.”

He thinks momentarily. “I'd like to be able to think a bit more beyond death. Perhaps that's the next project. As Montaigne said, it's the job of philosophers to learn how to die.” Nothing too ambitious then, not after you've just started rewriting 22 million words.

Raymond Tallis's Hunger - The Art of Living (Acumen Publishing Ltd, £9.99) is available in paperback at £9.49, free p&p, phone 0870 1608080; timesonline.co.uk/booksfirstbuy

The think-tank

5am time Professor Tallis starts writing

135 of his literary manuscripts were rejected before his first prose book was published in 1987

30 According to Tallis, we laugh 30 times more when with people, than when alone. For madmen, this is reversed

15 The age at which Tallis declared he was a “biochemical materialist”

120-150 His prediction for the future life expectancy of human beings

Source: Times database

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