Does the Labour Party have any chance of winning the next election?
I don't think the outcome is certain, despite the polls. It's foolish to forecast anyway. I believe the more difficult the circumstances, the more people will be inclined to trust those in charge at the moment. The trouble with all political discussion is that it's about individuals, and I'm famous for saying it's issues that matter . . . Can I puff my pipe, will that worry you?

No, please do. What tobacco do you smoke these days?
At the moment, St Bruno is my patron saint!

How do you stay so physically and mentally fit?
Well it's not a good day to ask this, as I am a bit low, having just come out of hospital. But I've got an interest in life, a lovely family and colleagues I like, and I'm very, very busy.

Do you ever feel like you can't be bothered?
No, because I think that would indicate that you didn't really believe in something. The feeling that it's too much, maybe, but never a sense that I wish I didn't have to do it, because I'm driven to do it. I enjoy achieving things.

Is politics a noble pursuit?
I have found it very satisfying. If you are an MP, you are employed by your constituency, and you have a responsibility to them, to your colleagues, and to your conscience. You have to reconcile these things. It is very hard work.

What is your greatest achievement?
All your so-called achievements in politics depend on millions of other people, so I'd like to be remembered as somebody who encouraged people. And on my gravestone, "Tony Benn: he encouraged us" would be a wonderful thing.

What would you like to forget?
I don't think one ought to forget anything. I've made every mistake - but mistakes are how you learn. The only thing I would be ashamed of is if I thought I had ever said anything I didn't believe in, in order to get on.

What about mistakes you made as a minister?
When Atoms for Peace came along I was persuaded that nuclear power was a cheap, safe and peaceful use of atomic energy, and my experience of running it as a minister was that I was wrong on all fronts: it's really about the bomb.

Do you vote?
Yes, I have always voted Labour.

What would have been your first priority, if made leader of the Labour Party?
I think it would have been to try to bring the left together. There are all these left parties, all arguing over a small section of opinion. You have to try to build support around causes. It is uniting to campaign on a single issue, and it is never just a single issue; it's always more than that.

Your first ministerial post was as postmaster general. What do you think of today's strikes?
I support the postal workers because I think the idea that a public service such as the Post Office can be treated on a competitive basis is ludicrous. The companies competing with it are cherry-picking. The Royal Mail is our oldest public industry - established in the 1600s - and the destruction of it is a very serious mistake.

What is the most precious piece of advice in your new book, Letters to My Grandchildren?
I have always tried to approach young people with respect. Old people often lecture them. My generation made a complete hash of the world. Young people today are the first generation in human history with the technical capacity to destroy the human race, but also the first with the know-how to solve its problems.

Where is your favourite place in the world?
My family home in Essex, a prefabricated house that my grandfather bought in a catalogue for £635. They floated it upriver on a raft. I've spent holidays there almost every year of my life.

Is it true you bought the bench on which you were sitting when you proposed to your wife?
Yes, it used to be in the front garden of our London house. Now it is in Essex, where Caroline's ashes are buried. I was a bit shy: it took me nine days to propose to her after we first met.

Are you perhaps as much a romantic in your political life as you are in your personal life?
I think if you're going to be committed to doing anything, you really have to care about it, and I suppose that is a romantic idea.

Is socialism dead?
When people say it is, I think of the NHS: it was the most socialist thing we ever did, and also the most popular thing we ever did.

Are we doomed?
No, I think the future is what we make of it. If you give up hope, you are surrendering the future to other people.

Tony Benn's "Letters to My Grandchildren" is published by Hutchinson (£18.99)
Interview by Emily Mann

See more photos from the exclusive portrait shoot by renowned photographer Philip Sinden here