WHY did Glenda Jackson do it? No, not take her clothes off in Women in Love; that was because the part demanded it. The bigger question is why she threw up a career that had given her two Oscars, countless Actress of the Year awards, plus great dollops of fame and fortune, to become a humble backbench MP. Was it because her life demanded it? I bet that's what she'll say.

She'd just come from a Girl Guides meeting, which happens to have its world headquarters in Hampstead, her constituency, so naturally, she was there as the local MP, celebrating the birthday of Lord and Lady Baden-

Powell. (Each was born on 22 February. Not many Guides know that.)

'The Guide movement seems to have changed quite a bit since I was in the Brownies during the war in Hoylake,' she said, referring to a couple of Guide booklets she had been given. One was on Aids and the other on street children.

Deadpan delivery, no trace of a smile. But I smiled. No trace of any artifice. Not even your eyebrows, they look a bit plucked to me? 'It must be your eyes,' she said, as we went off for lunch.

She's never worn make-up, in real life, and very little jewellery. Today, she is wearing ear-rings, plus a brooch, but no rings. When she was married, from 1958-1976, she did have a wedding ring for a while. She lost the first when she was with Dundee Rep and her part as an unmarried mum called for no ring, so she used to leave it in the dressing room, till one day by mistake she threw it out in the waste bin. The second she lost while gardening. Since then, her fingers have been naked.

Elegant woollen suit in a sludgy colour, well-washed sensible hair, poor teeth, but a great face, such life, such intelligence, such purity. Can I smoke, she said. No, I said. I get asthma. 'Oh, bugger it. Oh well, if I can last six hours without a fag in the House, I should manage to get through lunch.'

Her first reply, to why she did it, was that a London constituency came along, Hampstead and Highgate, so it meant she wouldn't have to move if she got the seat. She'd had approaches before, but didn't want to uproot while her son, Daniel, was still studying. Yes, but why be an MP, anyway?

'For 20 years I worked for the party, canvassed in three elections, worked myself into a rage because of Mrs Thatcher, watched the Tories savage the country. I wanted to help Labour win. Changes have to be brought about by government policy. You can't do it from the outside. Otherwise it's just sticking plaster.'

Hard luck, then, not to win. 'Yes, I did think we would. If you'd told me otherwise, I would not have believed you.' But she did take her seat from the Tories, by 1,440 votes. 'My emotions were all mixed. A strange night. A curious experience. After the result I just went home to bed.'

The following Monday, she presented herself at the House of Commons and asked for an MP's pass, which she got, an office, which she didn't, then she was given a tour of the House, with short cuts pointed out. 'I couldn't remember one of them. For the next two weeks I was still standing around saying 'Help, I'm lost'.' A friendly Scottish MP allowed her to camp in his office, but she still didn't have a phone or a secretary, yet from day one she was getting 100 letters a day. 'I can't type, so I had to reply to each by hand.'

It took her three months to get a small office, which she shares with another woman Labour MP, Tessa Jowell, plus their respective secretaries. She also has a part-time secretary who does two days a week, plus Daniel who acts as her research assistant. All of this help, plus office equipment, has to come out of her office allowance of pounds 38,000. 'The facilities for an MP are awful, but then I knew they would be. The hours are lunacy, and I knew that too. The library is amazingly good. That's something.'

In her third week she made her maiden speech, traditionally supposed to be uncontroversial, but she did manage to get a dig in at the Prime Minister. 'It was the most frightening speech I've ever made. It just suddenly hit me, being responsible for representing 60,000 people. And I was thinking of all the magicians of the English language who have lived in Hampstead. I kept on thinking of Keats, bugger me, he would have been one of mine.'

Since then she has made eight speeches, plus assorted questions and interruptions: four speeches on housing, two on railways, one on the police in London, one about the press and the right to know. But not one on the arts. 'It's not my main area of special interest. If you look at society's priorities, you can't says the arts is a fundamental one.'

Today, as she nears the end of her first year, she is still learning. 'There are areas I still don't understand. You ask a senior MP something and they'll say it takes 25 years to learn. 'I haven't got 25 years,' I say. 'Just give me a hint'.'

Has she been impressed by any speakers, not necessarily for content, but as performers? 'There was a splendid speech last week by Aldridge Brownhills. That's his constituency. Hmm, not sure where that is. He's a Tory called Robin or Robert Fletcher. (Try again, Glenda. He's actually called Richard Charles Scrimgeour Shepherd.) Anyway, he was splendid. He talked about the right of we the people to information.'

What about the social life? 'It looks like a big beehive, but then everyone scurries back to their cells. I had expected more social contact.' She hasn't found it too laddish, which is what many women say. 'I've always worked in a business dominated by men, so that's nothing strange.'

Nor does she moan about the lack of attention backbenchers get. 'I've submitted questions for the Prime Minister every week since I arrived, but as a backbencher I know I have to take my chance. I've been lucky twice so far. But I have learnt you must study carefully the questions chosen, find an angle to do with your constituency, then you have a good chance of getting in with a supplementary if you catch the Speaker's eye.' Ah, so that's the trick. 'No,' she said in her coolest, headmistressy voice. 'That's the system.'

So far, she'd answered every question but curtly, grimly, under sufference. Ah, a smile at last. 'My office is round the corner, in Parliament Street, so when the division bell goes, I have only six minutes to get into the House. When I hurtle there during the day, this big policeman lifts up his hands, stops the traffic, until I cross. That is amazing.'

Big grin, then back to her serious, 'I am a dedicated backbencher' mode. She's kept her head down, out of the limelight, deliberately not doing television or giving interviews.

In her acting career, she never looked or behaved like an actress. No star could have been less lovey. Now in her political role, it would be hard to see her kissing babies, drinking pints, listening to bores grinding on. As ever, she makes it clear she is a committed person, there to work.

All the same, are you enjoying it, so far? 'What I would enjoy,' she said sharply, 'would be one moment when I wasn't looking at the clock and when I didn't have a phone to answer. That has not happened yet.' But you know what I mean. 'I don't. People asked me if I was enjoying myself as an actress, as if acting was some pointless game I was indulging myself in. It's a job of work. Like being an MP.'

All right, forget the fun. Do you feel you have done any good? 'I think my constituency surgeries are very worthwhile. It throws me into a context I could never have got otherwise, with new people coming to me all the time with their problems. It's hard to work out how much good is done, but as an MP you do have power to help people by getting answers out of government and other organisations.'

Yes, but Joe Bloggs MP can do all that. You happen to be a well-known person, who had a huge success in another career. 'I don't call it a career. It was just work. Sometimes I was in work. Sometimes I was out of work.' OK, but you could have used your name and contacts and experience to better advantage, running a charity, some action group, helping society as a whole.

'I've told you earlier,' she said, sighing. 'The only way to change things is through political power. Yes, it is tragic we are not in power, and it's tragic that Neil Kinnock did not become PM, but I hope you are not suggesting there is no role for an opposition party in a democracy . . . ?' Of course not. But you're 56, with another four years in opposition. At least. 'I plan to stand again, and I hope to be re-elected, and this time we'll be in government. So I'm looking 10 years ahead. That's enough for the moment.'

But don't you get depressed and feel impotent? 'I am angrier, if anything. I now see the Government mouthing its inanities in the flesh. There is too much work to do to be depressed.'

Would you ever return to acting? 'No.' Were you fed up with it anyway? 'I'd lost faith with some of the people who had lost faith in the theatre, but that wasn't the reason I went into politics. Acting would have given me up anyway. Women are badly served by writers. It's hopeless for the middle- aged actress. I wasn't going to hang around all my life waiting to play the Nurse in Romeo and Juliet.'

She misses nothing about acting. She has not been to the theatre for two years, or the cinema. 'I haven't seen Howards End and don't want to. I'm sick to death of nostalgia. All we seem to make is films about a Golden Age, which wasn't very golden anyway.'

She still lives in Blackheath, her home for 30 years. She did think of moving to Hampstead, but fears selling and then buying could take her six months, and she hasn't got the time. Daniel, 23, lives with her. 'I throw him two clean sheets once a week, and leave him to it. His room is a health hazard.'

Last year he lost an eye in a public- house incident, trying to help someone. She says he is bearing up well, considering. 'It so happens that he has an uncle who lost an eye in a car accident many years ago. He's led a normal life, so that has helped.'

She doesn't see herself marrying again. After her divorce she did live with someone for five years, but for the last 15 she has lived alone. 'I couldn't now make adjustments to my physical living space.' What if True Romance came along? 'Ah, we can't legislate against being swept off one's feet, but I can't see it happening . . .'

(Photograph omitted)