'PERSONAL ASSISTANT to show business personality,' read the advertisement which caught Norma Farnes's eye back in 1966. Norma, who was sharing a flat in Kensington with three other girls, decided to apply. When she was told the personality was Spike Milligan, Norma got cold feet. She remembered the stories about Spike from her time at Tyne-Tees television where she started her working life in 1959. The agency assured her that he was really a very nice man. 'Well maybe he is,' said Norma, 'but I don't want to work for him.' She arrived for her interview on a bitterly cold day. Spike was sitting behind the desk in his tiny office, wearing a woolly hat and a polo-neck sweater.

The French windows were wide open, and there was no central heating. 'The first thing I said was "It's freezing in here." And he said, "Yes, I know. I don't like Americans."' Norma was momentarily perplexed. Then the penny dropped.

'I thought, "Shall I tell him it was the Italians who invented central heating? No, best not to!"' On top of the filing cabinet, Norma noticed three cartons of Swoop (wild bird seed). Suddenly, half a dozen pigeons swooped down on the window ledge.

'Good morning, lads!' said Spike. He began to introduce them to Norma: 'This here's Hoppity, he's only got one leg...'

'I thought, well he's a bit odd... but he can't be all that bad if he feeds the wild birds.' Then Spike said, 'You're awfully thin, aren't you? You've got legs just like Olive Oyl. I wonder who'd want to make love to an elastic band...'

Norma fired back, 'Another elastic band.' 'You'll do for me,' said Spike.

Norma was plunged into the anarchic world of Number 9 Orme Court, where Spike and other great post-war comedy writers like Eric Sykes (who is still there), Johnny Speight, Galton and Simpson had formed a writer's cooperative. She planned on sticking with the job for three months, but stayed with Spike until his death 36 years later. Over this time she became his agent, manager, confidante and loyal friend.

Now aged 71, Norma Farnes is a warm, elegantly attired lady with a quick Yorkshire wit, and a breezy, infectious laugh. Her large ground floor office in Bayswater, where she has been based for forty years, is a fitting testament to the life of one of our funniest, most creative entertainers. Photos and mementos of Spike and his friends pepper the walls (Spike with Eric Sykes, Prince Charles, Peter Sellers...) The room is a museum to his memory, his larger-than-life personality permeating the place to such a degree that it is hard not to sense the emptiness left in his void.

Norma sits behind her desk with its antique telephone ('gift from Spike') and affectionately reminisces about her late employer, a man who was by turns notoriously difficult, delightful, a tyrant, compassionate, and capable of great acts of kindness. The manic depression that famously defined Spike Milligan's personality manifested itself early on in their working relationship. Norma quickly learnt that the best way of coping with 'Spike's rantings' was to ignore them.

'One night,' she recounts, 'Spike was screaming about something or other, and I thought, I can't be doing with this, I'm going home. The next morning Ray Galton said to me, "I think you'll stay here... You've got the Scarlett O'Hara attitude: I'll deal with it tomorrow."' On another occasion, Johnny Speight walked in during one of Spike's bawling sessions and said, 'He's not shouting at you, you know, Norma, he's shouting at the world.'

Then came the 'black dog' depressions, when Spike would lock himself away in his room, sometimes for days. In the late 1960s and '70s, when his depressions were deeper and longer, he would not emerge for weeks. Norma would slip little notes under his door: 'I'm going home now; I'm at the end of the phone if you want me.' She always made sure she left a little bit of the note out so she could see if he had read them or not. After a time, she would see the notes disappear, only to re-emerge moments later with the message: 'Fuck off and leave me alone.'

'It was then that I'd know he was coming out of it, because he was getting the energy to tell me to bugger off.'

The worst time was when he asked Norma to shoot him. 'His room was boiling hot. It was like walking into India. He had about five of those awful little two-bar electric fires going. The heat was unbearable. He said "I can't ask anyone else, and I can't do it myself." He had a gun, and he was deadly serious. There was no audience. It was just him and me in this hot, hot room. I said, "No Spike, I can't do that..." He was crying. It was very sad. We talked and talked for hours. I said, "What would it do to your mum? What would happen to your children?"

'Eventually he fell asleep and I went home. A friend said, "Did you never think he would shoot himself once you were gone?" But I never did. I felt the time had passed. He'll be alright now, I remember thinking.'

We talk about Spike's close friend Peter Sellers, a man who by all accounts was even more of a monster than Spike. 'Though Peter could be very kind, too,' says Norma. 'When I was going through my divorce he was just sensational. He called me and said, "Oh, Norm! I'm so upset, you're getting a divorce... Spike tells me you're having a bad time..." I said, "Pete, I'm having a terrible time and I don't really want to talk about it." Then Peter said, "Look, I just want to tell you, the first divorce is always the worst."' Norma laughs at the memory. Sellers even offered her the loan of his boat for a few days. 'Take yourself off to Capri,' he told her. 'You'll feel better.'

'That was the good side of Peter. The bad side was horrendous!'

Norma tells the story of Spike's old Austin Cambridge 'Min', a motorcar he was so devoted to he would refer to it as his best friend. 'Peter adored it, too, so Spike said, "Oh, let him have it." Then Sellers had the whole thing re-done, all the leather re-upholstered at great cost, and gave it back to Spike as a present. The car went back and forth like you'd never believe. I never knew who had it, or where it was! But in the end it remained with Spike.' That is, until Sellers failed to get an Oscar for his performance in Being There (it went to Dustin Hoffman for Kramer v Kramer). 'All Peter ever wanted was an Oscar, so he was devastated,' explains Norma. Spike was touring in Australia at the time, and during a live phone link-up between Sellers, Milligan and Irene Handl, Spike jested on-air, 'You didn't get the Oscar then! Ah, Pete, you were caught with your trousers down!' Peter Sellers was so furious, he sold Spike's beloved car behind his back.

When Spike returned from Australia and found out what had happened, Norma, ever the whipping girl, got the blame. 'What else have you given away while I was away?' he ranted. 'My family? Have you given them away? Do I still own a house?'

'He went on and on,' says Norma,

'I said, "For Christ's sake, it's your best friend, it's your mate that's sold the car, not me!"'

Did the rift last long?

'No. Spike would always forgive Sellers and vice versa. It was a very strange relationship. Very, very close. They could complain about the other to me, but if I said anything about either of them, Sellers would say, "Well, you know, he is the genius, the most creative of all of us."'

Did Norma share this appraisal?

'Oh, yes. Peter once said, "I was just a vase of flowers, and Spike arranged me."

I thought that was about right. Though I do think Peter would have made it anyway because of his wonderful gift for mimicry. He could be quite frightening. If you sat opposite him for five minutes, he'd take on your persona. Eric [Sykes] didn't like it, and neither did Harry [Secombe]. It was eerie. Eric tells me a story about a mutual friend of theirs who had died a few days earlier. They were in a restaurant when Peter started to impersonate the dead man, and Eric said, "Give over, Peter, it's not the right time..." Peter could just change into a different person. He even started to look like this person.'

Our conversation steers inevitably back to Spike Milligan. I mention a piece I came across in the Guardian describing him as a neo-racist (yet he refused to play to white-only audiences in South Africa). 'Spike was not a racist,' says Norma, emphatically. 'He was concerned about the dangers of uncontrolled immigration... He called it "the beginning of the end." It started when they built the mosque in Regent's Park. Spike said, "I wonder if they'd let me build a Roman Catholic Church in their country?" I'd say, "Oh, don't start all that again, please! They've got to have somewhere to pray!" Then he'd say, "Well, it's not right... They can come here, of course they can, but they have to accept how we are." If someone upset him and he was an Indian, he'd say "bloody Indians". Spike adored Italy, he only ever really ate Italian food. And he loved the Italian people. But one phone call, say, to an Italian telephonist who wouldn't put him through, it would be "those bloody Italians!" He treated everybody the same. People interpreted that as being racist, but he really wasn't.'

Who were Spike's comedy heroes? 'Groucho Marx,' says Norma without hesitation. 'He absolutely adored him. And Buster Keaton. He wasn't keen on Charlie Chaplin. Eric's not either...'

Of the new generation of comedians, Spike, perhaps unsurprisingly, loved the surreally inventive Eddie Izzard.

I wonder what Norma misses the most about Spike?

'Oh, the laughter. And the flowers... Spike was a great flower sender.'

* Box 18: The Unpublished Spike Milligan, edited by Norma Farnes, is available from The Oldie Bookhop for £16.50 (RRP £18.99). Telephone 0870 429 5874 to order.