HOW MUCH do we really know - I mean really know - about Stella Rimington? That she rates a three-line entry in the latest edition of Who's Who and is the director general of MI5.

It isn't much, is it? However, these two scraps of biographical detail add up to more than we have ever known officially about Britain's spymasters. Together with the luncheon invitation to MPs earlier this week, they are supposed to constitute real proof that the Prime Minister is delivering on his promise of a more open policy on the security services.

Ever since the new head of MI5 was publicly announced for the first time in December 1991, the race to find out more about Mrs Rimington and what she does has been furious.

It has not produced a richly detailed harvest. Mrs Rimington appears to be little different from other professional women. She lives, apparently, in north London, where she has had a dispute with a neighbour over a garden fence. She shops at Jaeger, has two daughters in school and is separated from her husband.

Mrs Rimington is supposed to have risen to prominence as head of MI5's 'F2' division, which handles domestic subversion. As such, she was responsible for monitoring trade unions - a job which brought her to the attention of Downing Street during the miners' strike. No one at the agency's headquarters in Gower Street, WC1, will confirm this, but the so-called 'espionage experts' repeat the assertion nonetheless.

Some say she was also the overall boss of Operation Flavius, which ended when three IRA 'players' were shot by the SAS in Gibraltar in March 1988. Others say she was not. Either way, she was never called to give evidence, although other MI5 agents were - from behind a curtain.

The single murky photograph of her which exists today shows a plain woman with short dark hair striding down the street in flat heels and a long coat of hound's- tooth tweed.

Is it surprising, given the paucity of detail even about this well-publicised figure, that so many myths still abound about female spies and what it is like for women to work for the security services? 'A lot of what is written about women and espionage is pure male fantasy,' says Julie Wheelwright, author of The Fatal Lover, a biography of the Dutch-born 'agent' Mata Hari, whose execution towards the end of the First World War sanctified her position as the ultimate spy-seductress. 'A lot of spies went on to write fiction - Somerset Maugham, the French agent Georges Ladoux, and Erskine Childers (who wrote The Riddle of the Sands). They couldn't write the whole truth, so they ended up romanticising it.'

What emerged from their imaginings were some of the 20th century's most enduring tales, some of them entirely mythical. First there is the spy as honey trap; 'courtesans' like Mata Hari and Vera Erikson, who was also arrested during the First World War on charges of spying for the Germans. According to her biographer, Ladislas Farago, Erikson was 'blonde, bewitching and had nerves of steel'. Then there is the spy as heroine: the brave patriot sent on terrifying missions, who in reality was often ill-prepared and given little back-up. The two most famous are still Edith Cavell, the First World War nurse, and Violette Szabo, better known as the heroine of Carve Her Name With Pride. John Le Carre had his Connie, and James Bond, of course, his Miss Moneypenny.

The impulse to perpetuate these myths still endures. Witness how reporters besieged MI5's headquarters during Mrs Rimington's recent lunch with MPs in an attempt to discover whether Lady 'M' really had souffle Monte Christo on the menu. Apparently, she did.

Far from the executive dining room, however, working for the security services is, for the most part, a very boring job. One former agent says much of it is routine, 'involving long hours of tedious paperwork'. The end of the Cold War, which eliminated the need for recruiting and running secret agents across the Berlin Wall, has only made it more so.

The two arms of Britain's security service employ hundreds of women. MI5, which deals with domestic security, has 2,000 staff and close to 40 per cent are women. SIS, which is more commonly known as MI6 and operates largely overseas, also employs a large number of female officers. According to Rupert Allason, the Tory MP and historian who writes about espionage under the name Nigel West, 'women have always really run the security services'.

They may not, until recently, have risen to the top, but they keep the operation working smoothly. The most important part of MI5 is its registry of files on potential subversives and other suspects. 'The key to the security services is the accuracy of their files and the ability of the people who work there to extract the information they need from them,' says Allason.

'Women are patient and painstaking and they do this job particularly well. The person who runs the files and oversees the 200 women who keep them up to date is known as the 'Registry Queen'.'

The women officers at MI5 are recruited as university graduates through the regular university appointments offices, or via promotion from secretarial jobs. Those who join young and then leave to get married are known as the 'debs'.

Those, such as Mrs Rimington, who sacrifice their personal lives to the job, are known as 'nuns'. In addition to Mrs Rimington, one of the eight members of the Security Service's directorate is a woman. She is believed to head one of the two 'K' divisions charged with counter-espionage. The head of the 'watchers' department, which runs MI5's surveillance and shadowing operations, is also said to be a woman.

Officers at MI6 work for the Foreign Office and are almost always university graduates. They are stationed in British embassies abroad, where they never rise above first secretary, although some unofficially hold ambassadorial rank.

All potential MI6 officers must sit regular Civil Service exams, but they have to be approached to join the agency. Oxford University history graduate Lucy Dormer only realised that her name had been put forward when, out of the blue, she received a letter from the 'Co-ordination Staff of the Foreign & Commonwealth Office'. It was then she remembered a woman at the University Appointments Committee had once mentioned that there were 'special jobs' in the Civil Service to which she might be well suited.

'I was called to an interview at 3 Carlton Gardens, one of the Foreign Office buildings, where I first had to sign the Official Secrets Act,' says Miss Dormer. 'I was ushered in to see a man I shall call Mr D. His office was small and painted white. There were two wooden chairs around a wooden desk with a plastic top. He was quite a jolly man.' The interviewer was quite open with Miss Dormer about what it was she would be expected to do. 'He told me a bit about what was involved in the job and then he asked me lots of questions; about my family, about what I thought of what was going on in Eastern Europe, in Poland, and about where I would like to be posted.

'He talked about the importance of looking out for potential agents in foreign countries. The best ones, he said, were people with weak personalities; people who were either greedy or had some grudge against their own regime. The way to get them was by bribery or persuasion, or by promising them asylum in the West.

'He assured me we never used blackmail. But the whole atmosphere was very odd and I found it hard not to burst out laughing.'

The secrecy involved and the prospect of not being able to discuss her job with her family put Miss Dormer off the service and she did not follow up the interview.

Other women join the service, then leave when they become either disenchanted or disaffected. Miranda Ingram, who now writes for the Daily Mail from Moscow, left M15 because she grew bored with the routine work. While Cathy Massiter, another M15 officer, left in the mid-1980s because she was unhappy at the agency's stepping up of telephone tapping.

Others are put off by the long hours and poor pay. According to Stephen Dorrill, co-publisher of Lobster, a twice-yearly newsletter on spies, the security services 'have become a ghetto for women'. Dorrill devotes a long chapter to women agents in his new book The Silent Conspiracy: Inside the Intelligence Services in the 1990s, which is due out in March. He maintains that working for MI5 and MI6 has become 'more like working for the social services. A lot of people have left, especially men. The services find it hard to recruit good staff. People look at it and think, 'If I really want to make it I'm better off going into industry or the City'.'

As the climate in which the security services operate begins to adjust to the post-Cold War world, both MI5 and MI6 are having to find new areas to explore. For MI5, this has meant taking up much of the anti-terrorism work done by the police, especially against the IRA. For MI6, says one former officer who maintains close links with his old colleagues, it has meant stepping up commercial and economic espionage - 'on bank deposits, oil deals and the European Community'.

For Mrs Rimington, who is the first woman in the world to head a major security service, there is another challenge: to kill the myth of Mata Hari and yet maintain the attractions of a job in what is known as 'the business' for intelligent women of the next generation.

(Photograph omitted)