The plaque outside the Sixties breeze-block house in Sussex commemorates ‘The Blind Architect’. In the sitting room a notice reads: ‘No smoking. Trying to give up lung cancer.’ And the invitations displayed on the shelf are mostly for parties in 1988. This is, after all, the home of Spike Milligan, 74-year-old former Goon and manic-depressive.

Milligan has sad eyes, yellowing hair and looks old and frail as he shuffles to sit down, joking and charming, wearing slippers and jeans. Almost immediately he accuses me of wasting the world’s resources with my research notes. Yet this week sees the publication of a 213-page book, Depression and How to Survive It, a collaboration with psychiatrist Dr Anthony Clare.

Milligan first identified himself as a manic-depressive on Clare’s Radio 4 programme, In The Psychiatrist’s Chair. Nearly 10 years later, Clare has taken Milligan as a case study in this book to help fellow sufferers. Milligan, who has suffered from depression for more than 40 years, has written ‘maybe 47 books’. He’s just finished a satirical version of the Bible and is currently writing a comic adaptation of Wuthering Heights, with Heathcliff cast as a Pakistani.

I felt nervous interviewing him. He’s renowned for his passionate outbursts, possibly using his illness as an excuse for intolerance and insensitivity. He’s crazy about punctuality, taking lateness as a personal insult. He went into a tirade about overpopulation when he learned of Clare’s seven children, despite having five of his own – but they were born before he became concerned about the environment. ‘In my view,’ says Milligan of Clare, ‘he’s ill.’

Milligan was once given a conditional discharge after firing an air gun at a 15-year-old who climbed over his wall. Another time, he threatened to kill Peter Sellers with a potato peeler.

Speaking to him feels like walking on egg shells. ‘I don’t like people,’ he says. ‘They’re hateable, stupid and boring.’ His eyes blaze and his voice rises. There’s been a misunderstanding. He hadn’t intended to include his third and current wife, Shelagh, in the view that, ‘even the best people can turn out the worst. Even dearest ones can turn on you’.

The same reaction occurs when we talk about his fifth child, the product of an affair in the Seventies when Milligan was married to Pat Ridgeway. Following revelations last year by his ex-lover Margaret Maugham, Milligan met his illegitimate son, James, 17, for the first time.

He says, without emotion: ‘Meeting him was just like meeting a new person. We sat down and had tea. I asked him about his schooling, which I pay for. I asked him about religion. He’s not much into religion.’

Milligan’s illness has impinged on all aspects of his life. Clare notes a significant association between manic-depression and Milligan’s comic genius; but he’d willingly give up his fame and achievements to be free of the agonies of his illness.

‘If I had my time again, I’d like to come back as a tree.’ Then, typically quirkily, he considers dogs’ urine, and decides he would prefer to be a Greek philosopher.

Milligan, patron of The Manic-Depressive Fellowship, was in the middle of one of the worst depressions of his life while working with Clare. ‘I wanted to kill myself with pills. What stopped me was the thought of my family. I could see that haunting spectre of them standing over my coffin crying their eyes out.’

He has suffered at least a dozen breakdowns. Has he ever feared going mad? ‘I’m too intelligent for that,’ he says, fiercely.

What is his current state of mind? ‘Like an aeroplane. I don’t fly too high and I don’t go too near the ground.’ He’s on drugs to stabilise his condition. ‘Nobody knows the side-effects. I might go purple and one leg drop off.’

Six months ago he had ECT (electroconvulsive therapy). ‘When the nazis did this it was seen as cruelty. I used to wake up and not know who I was and didn’t care.’ His eyes light up when he says he’d like a portable ECT machine to put himself to sleep immediately when people’s conversations bore him.

He has had no ongoing relationship with a psychiatrist, possibly because, in Clare’s words, he’s a great ‘faller out’. ‘I haven’t fallen out with anyone,’ he refutes. ‘I’ve had people fall out with me.’

Milligan believes he inherited his hypersensitivity. ‘My mother was highly strung. I remember seeing my grandfather in a rage, striking a servant.’ Clare considers Milligan’s temperamental parents, absent soldier father and domineering mother, as causal and aggravating factors. He thinks his illness began after being shelled during the Second World War. ‘My life was like an egg in a shell, just waiting for someone to crack me open and fry me. A bomb dropped right near my head. I got battle fatigue. The war fried me.’

For six years during the Fifties he churned out 26 scripts a year for The Goon Show. ‘It was driving me mad. I had a nervous breakdown. It’s like a roaring pain. The loudest pain you’ll ever get.’ The photo-grapher’s camera winds on. ‘What’s that, for God’s sake?’ he snaps, literally driven mad by noise.

His latest depression was brought on by his mother’s death. Among her last words were: ‘‘We’re not like other people.’ I think it’s true,’ he says. ‘I just don’t get on with them. People don’t write the comedy or poems that I write.’

He is now in the winter of his life, an Irish Roman Catholic who ‘no longer’ believes in God. How does he regard death? ‘Hugel’s Gewurztraminer is as far as I go towards heaven!’

Is he frightened of dying? ‘I used to be terrified of it. Now it’s getting closer, I don’t really know. I know it’s going to happen one day – the one day I’m trying to avoid! In 100 years I’ll be forgotten, except for my overdraft at the Midland.’

He shows flashes of kindness and plays at being gentle. I felt sorry for him, although he’s also rude and unforgiving. Clare describes him as sensitive, easily hurt, vulnerable, a perfectionist who is profoundly nostalgic and actively charitable.

‘He’s difficult because he can be persistently demanding,’ says Clare. ‘He’s ‘for’ and ‘against’ things very fiercely, which I’m not. That caused tension. But it was compensated for by his anarchic sense of humour.’ Clare’s analysis of him in the book is, says Milligan, accurate as far as it goes. ‘But it’s difficult to get to the inside of someone. All of us keep a secret we don’t want anyone to know until we die. I have something I won’t tell anybody because I’m ashamed of it. It’s something moral, something physical.’ He may be teasing, of course.