Only one man - Tom Baker, 61 - knows the truth behind the deceptive image of the best liked Dr Who in the famous TV series. As recounted in an interview in Saturday's Weekend magazine, Baker became a monk for six years, had s failed first marriage and once attempted suicide. When he was chosen as Dr Who, the former National Theatre actor was labouring on a building site and living in one bare room after giving away all his possesions. Today, in the first part of an extract from his autobiography, he tells how, dazzled by overnight stardom, he 'went mad'. This is his extraordinary story.

The totally unexpected thing about Dr Who was that a children's hero proved so fascinating to women - especially those whose tastes were, well, unusual. On our tours around the country promoting the series, I kept getting pulled by keen female fantasists.

As a younger man I had kept strict vows of self-denial and celibacy. Now, I had never been so sought after.

One young university don persuaded me to show her my Dr Who costume - and put it on herself. She looked terrific as she threw herself wantonly on the wide Holiday Inn bed and growled: 'Come on Doctor, let's travel through space.'

She really did say that. I nearly laughed in her face. But then, we were not in our right minds at the time and we had been drinking champagne. I managed to travel as far as the bed. As we grappled like demented stoats, her wearing my gear, I kept thinking I was making love to myself. At least she didn't want to whip me, as some Who groupies did.

It was all a far cry from the London building site where I was working as a labourer when I landed the role in 1973. By that stage I was a failed monk, husband and scorned jobless actor. And my actress girlfriend had called from Birmingham to say she had found 'great love with a man.'

The pain was exquisite. Things got worse when I played Hamlet for O-level children and was booed the first night, then pelted with marsh-mallows at subsequent performances. In despair, I gave away all my possessions, wishing for death.

Then one day in the warm little world of a pub called the Fox and Hounds, whose landlady, Diane, was the Mother Theresa of licensed victuallers, I was told to go to Elbury Street the next day at 7.15am and stand outside number 182, where the young Mozart wrote his first symphony.

There I would meet a man, Arthur Cordes, who needed a labourer. The work was menial, with no security, and the wages were the legal minimum. In deep apprehension and joyous depression I met Arthur, who led me to a building site near Mozart's place, gave me a cup of tea and a piece of bread pudding the size of a half brick and set me to work. Fuelled, I set to work, happy that nobody knew where I was or even cared.

The work was so hard that it soothed me. Being shattered at the end of each day helped me get through the night. As it sank into my poor nut that sheer bone shaking activity was good for me, I redoubled my efforts and always asked to take the Kango drill.

Using the Kango without ear protection for three or four hours a day took away any fears of death and memories of old loves finding new loves in Birmingham. But drilling left my arms shaking so much that I couldn't eat properly. I had to put my bread pudding on the floor and get on my hands and knees to it, sipping tea from the same dish. Some years before I'd been in The Millionairess with Maggie Smith, for the BBC's Play of the Month series.

Directed by Bill Slater, it was a success despite my not very good impression of Peter Sellars doing a foreign doctor. Now sleeping on a mattress on the floor of a room in Pimlico, London, I remembered Bill and wrote him a desperate letter: there had to be some part for me in the BBC's huge series and serials department.

That letter was written on a lonely Sunday night - Sundays have always been bad for me. Often I've drafted a suicide note on a Sunday evening. I psted it the next morning, on my way to the building site.

My poor begging letter reached Bill Slater's office on the Tuesday morning, after he'd left for a meeting with Barry Letts, a senior serials department producer.

Jon Pertwee had given up his hugely successful role as Dr Who, so Barry Letts and colleagues were discussing a successor. That was the first coincedence; the second was that Bill Slater was about to become head of serials.

It was 11.15pm and I was lying on my mattress, three-and-a-half miles away, when Barry Letts rang, setting up a meeting for the following day.

Barry and Shaun Sutton, head of drama, were nice men who seemed pleased to see me the next day. Someone fetched a glass of beer but I couldn't drink it. They said they 'had an idea' and asked me back the following day.

At work on the site, I mentioned that the BBC was considering me for some job. That started the teasing that actors get between jobs, getting referred to as 'Sir Laurence' and having the mickey taken.

I rushed home for a swill and a change of clothes, and took the Tube to the TV Centre, arriving a bit late. Back in Shaun Sutton's office, Barry Letts said: 'Tom, we'd like you to be the next Dr Who. What do you think?'

Dr Who was a plum job in television, I was living on the smell of an oil rag and bread pudding. All I could do was nod. I couldn't stop nodding. They laughed kindly, we all shook hands and I felt reborn.

Arthur and my workmates were amazed. On my last day at the site, I swore eternal friendship with everyone before I tottered off past Mozart's house, full of tears and good resolutions.

I never saw them again. I was Dr Who now. I was an alien.

The enthronement of the new Dr Who took place at TV Centre when I was presented to the Press. I wore a white suit and a Peruvian sweater and a painted tie. There was clapping, there was the flashing of cameras, and I hoped it would never stop.

I whirled and posed and smiled and looked alien, and the more they gasped, the more I did it. Everyone wanted to touch me and I wanted them to touch me, too, and it was just marvellous.

After signing the BBC contract, things hotted up. From all directions chaps wanted to discuss projects, and girls looked at me in a meaningful way. Plenty did more than flirt. Once I accepted an invitation for coffee in someone's hotel room. She seemed so proper and serious when she asked me up. Several large gins later I entered her room for that coffee, which became a green chartreuse.

After a couple of sips and with few clothes left on, I noticed a Bible on the bedside table with a whip laid across it. These scenes scared me a bit. I didn't like the whipping to be to fierce and I cheated on the bondage, always making sure I wasn't to tightly bound.

Several of these women wanted to whip or cane me. For most it was probably a punishment for my performance, so I couldn't complain too much. But when it was my turn to be spanker, my passion faded a bit.

Before starting Dr Who I made a film and met a very different kind of girl. Marianne Ford was marvellously amusing and very good to me. When filming finished I went straight into rehearsals for the title role in The Trials of Oscar Wilde at the Oxford Festival, and Marianne came with me.

thanks to her we were sometimes very happy over the next few years, and the times we were unhappy were all my fault.

I went to live with Marianne in London's Notting Hill Gate and at first we were happy. But the programme's success brought temptation after temptation from those curious females wanting to lay a Time Lord. It had very little to do with me at all. How could it, they were strangers?

When I'd given up the monastic life after nearly six years of prayer, and especially chastity, I had been slightly disabled in a way - too timid to mix easily or even go into restuarants - and after years of prayer or silence, it took a while to speak an English which people could understand.

Afterwards I couldn't get enough of people. Looking back, I tried too hard, and though some people quite liked me, something also repelled them. 'He's quite nice,' I heard a woman say, 'but there's something odd about him, something disgusting.' I still have that effect on quite a lot of people I meet.

That seemed to have changed when I became Dr Who. I didn't spot the falseness. Thinking , myself genuinely irresistable, I gave in to most of the female time travellers.

Marianne was very patient, and she may have thought that the madness would pass - but it didn't. And so I hurt the very person who was protecting me.

At the beginning, the programme and the role were my greatest concerns. All that was required was an ability to speak gobbledegook with conviction, which I found easy because all my life, including the years in the monastery, I had been taught nonsense by priests and teachers, on all sorts of subjects.

After getting to know Liz Sladen, who played my assistant Sarah-Jane, and other regulars on the programme, work became full of fun.

Towards the end of my run as a Time Lord, Lalla Ward took over as my new assistant, Romana. She was marvellously witty and good to be with that I fell in love with her. Our wedding, in 1980, made the national news. How we laughed. For a while the terrors of real life were eased by my marriage. I was comforted in my anxiety by Lalla's steadiness and wonderful wit

But Lalla is more intelligent and serious than I am, and she didn't need the low life I was enjoying. After a while I realised that I prefered the smoky comfort of the Colony Room in Soho - where I drank with Jeffrey Bernard and the painter Francis Bacon, among others - to the domesticities of life at home with Lalla.

Our relationship was not moving in any direction. Drinking heavily, I wasn't going anywhere accept Soho. It was a mad and dangerous time for me, and it could not continue at that pace, but I didn't care. I was just waiting for something to happen.

As it did. One evening in the middle of 1982, following 16 months of marriage and after a gentle, kind, and quite short conversation with Lalla, we parted. She had quickly realised that the home life did not nourish me and she very kindly made it easy to escape. We decided to go our own seperate ways and see what happened.

We never saw each other again.

But then, a blighted marriage was no novelty for me. Years before trying - and failing - with Lalla, the self-destructive insecurity rooted in the loss of my faith on leaving the monastery had led to the loss of my first wife and two sons. Driven to desperation I tried to kill myself and then my mother-in-law.

The BBC missed the opportunity to make two programmes for the price of one - our rehearsals and arguments would have made excellent light entertainment.

The chaps playing the Daleks wore their top bits at rehearsal. During threatening scenes, they held out their right arms in place of the regular sink plungers. They all took it highly seriously which, of course, only added to the fun.

Very often the cast of Z Cars crept into the back of the rehearsal room and watched with delight. My turn-of-the-century style of pretending to be frightened reminded Frank Windsor of his great-aunt Mimi who never married because she was scared of men. whom she saw as aliens. I was very flattered by this.

Dr Who performers were often more fascinating than characters in the script. Michael Wisher, who played Davros, for example. rehearsed while wearing a kilt, with a paper bag over his head - maintaining his feel for the part. (Davros, for those who don't remember, wore an ugly mask - through which Michael couldn't see - and had no legs.)

He took his part so seriously that he would not remove the bag, even during breaks. to see coffee and biscuits being pushed under the paper, followed by a cigarette, while the bag kept expressing Davros's feelings about things, was bliss. He did allow us to make a hole in the top of his paper bag, though, so that smoke could escape.

For one Cybermen adventure, I proposed it should start with a clip from a Fred Astaire movie. The idea was that the Cybermen had got hold of an old musical and admired his style. Naturally, they also liked Ginger Rogers, who did everything Fred did, while travelling backwards on high heels.

Cybermen moved as if their knickers were twisted, and tightly twisted, too. It would be funny if we started on a clip of Fred and Ginger before panning across to Sarah-Jane and me, tied to a post. We'd be challenged to teach the Cybermen to move as gracefully as Fred and Ginger.

Bob Holmes, the deadly professional script editor, did laugh - then filled his pipe in order to create a smoke screen while he turned down the idea. Most of my suggestions were rejected and I got used to it. One can get fond of almost anything, even rejection.

After more than 120 episodes I felt so proprietorial about the Doctor that it was hard to take direction notes from the directors. During the shooting of the story Planet of Evil, I had to seize a poor alien at knife point. When the knife was offered to me, I felt disgusted by the idea of such a coarse threat in our lovely programme.

'Take me to your leader," I said when the camera rolled, 'or I'll kill you with this deadly jelly baby' (an orange one, my favourite). The director wasn't thrilled.

But when I asked producer Philip Hinchcliffe about the rushes, he answered: 'Oh, terrific, really fantastic. I loved that bit with the jelly baby.'

A few weeks ago, at a bookshop in Manchester, a boy of about ten offered me a jelly baby. He was so happy when I laughed, and he quoted the threat from that episode - my turn to be happy.

Who On Earth Is Tom Baker? by Tom Baker is published by HarperCollins on October 6 at 16.99. To order your copy, please telephone 0181 307 4052

This excerpt first appeared in The Daily Mail on 22 September 1997