Sara Keays has found a novel way to haunt the Tories
It's October, it's Bournemouth, it's the Tory faithful in full cry - and it's Sara Keays time once again. With her usual impeccable timing, she has chosen the middle of the Conservative Party Conference to launch her latest broadside into the heart of the Tory ranks - a novel of ministerial sleaze, officially-sanctioned blackmail and a well-bred innocent lady secretary under threat.

It's not, of course, the first time Ms Keays has chosen a key moment to embarrass the party whose favourite son did her wrong all of 13 years ago. On the contrary. Ms Keays has, over the years, so assiduously made a nuisance of herself that today she occupies a niche in Tory demonology and the national consciousness alike - as a feminised Banquo, a handmaiden turned avenging angel, the Home Counties Alex Forrest (of Fatal Attraction), the indefatigably smiling Wronged Woman of British Politics.

As the world knows, Cecil Parkinson was forced to resign from the Department of Trade and Industry in 1983 after his 11-year affair with Ms Keays came to light, along with the news that she was pregnant. Parkinson had been seen by some as the heir apparent to Mrs Thatcher; his career hit a temporary skid but he was back as party chairman by the decade's end. For Ms Keays, by contrast, it was the start of a war that still goes on. In 1985, she published her memoirs, A Question of Judgement, serialised in the Daily Mirror for pounds 110,000; Ms Keays's accusations about her suave former beau were splashed without mercy for five days.

The war opened a second front. Her baby, Flora, had suffered a brain tumour in infancy. The tumour was removed in 1988 and she started a lengthy recuperation, with special attention from paediatric specialists outside the UK. But over the child's blameless head, a whole legal campaign was fought. Ms Keays became a fixture in the news, popping up at regular intervals - to deplore, to complain, to win umpteen hundreds of thousands in libel damages and generally to stick a vengeful bodkin, again and again, in the Conservative Party's pachydermous hide.

In 1993, to deter the press from intrusive enquiries, Parkinson and Ms Keays jointly applied for an injunction to stop the media publishing any report identifying Flora as the subject of court proceedings, or indeed as their daughter. Although it was a measure to protect the child's privacy, it meant Ms Keays herself was effectively barred from discussing her ex-lover's maintenance record. In March 1995, Parkinson won a second injunction, banning her from talking to the media about anything relating to "the medical treatment, education, maintenance or financial circumstances" of Flora.

Now the Tories in Bournemouth can look forward to the newest instalment in this protracted drama: Ms Keays's first novel, The Black Book, published on Thursday (Doubleday pounds 15.99) and available for delegates to buy at a bookshop off the promenade (though it's unlikely Ms Keays will be around to sign copies). How much have they to fear?

Not, on the face of it, a lot. The core of the book is not, it turns out, the story of a handsome but neglected parliamentary secretary betrayed by a languid Trade and Industry Secretary with a Brylcreemed barnet and a clenched vocal delivery. It deals in scandalous goings-on at the Palace of Westminster, but they're the kind of scandals that would outrage the press (cocaine-snorting, paedophile rings, sado-masochism) rather than the armpit-scented personal scandals of betrayed love.

The Black Book is an artless piece of work, drenched in cliche and written without energy or ambition; indeed, it has the air of having been dragged from its reluctant author ("Come on Sara, one more chapter, you know you can do it...") like a series of dead wisdom teeth. Its author's celebrity as a socio-political victim is its sole raison d'etre. Had Ms Keays wished to write a roman fleuve set in the declining years of the Ottoman empire, one can imagine her horrified publishers steering her firmly towards Millbank and the Members' Lobby. It's set in the sweaty Echoland of Westminster; the time is now, the theme is corruption in high places.

Unlocking the Pandora's Box of the Commons is a young widow called Joanna, who worked as a UN secretary until her husband was killed in "the Balkans", as Ms Keays quaintly refers to the Bosnian conflagration, and picks up a job as PA to the government chief whip, Harry Hunter. Jo's CV is impressive enough to justify a seat on the Council of Europe rather than a position dunking a ministerial teabag, but she sets to willingly. Everyone is terribly kind, terribly helpful - so much so that every conversation in the book's first half operates to a rigid formula. All the women say, "Are you all right? Shall we have lunch?" whenever they see her, while the men (while mentally registering her frail beauty) say, "How're you enjoying it? Fancy a drink?".

Amid all this bleary socialising, Jo gradually twigs that something is up. Her boss changes, on the telephone, from a charmless bore into a teeth-grinding bastard, uttering proxy threats ("Oh he does, does he? We'll see about that...") and chuckling internally about his scurvy manipulations ("The Yanks have been trying to put one over on us and now we've got their chief European policy maker right where we want him, thanks to our obliging little in-House bondage freak..."). He also obligingly writes down the names of his victims on a notepad, so that Jo can read them later. She starts to wonder if the idealism of public service can become compromised by realpolitik, along with other blinding insights. Then she discovers the existence of the Black Book, the legendary ledger of MPs' misdeeds that is kept by the whips as blackmail fodder. She makes it public and becomes embroiled in a security scandal. Peace conferences, food shortages and unidentified viruses fly in all directions. The PM steps in. It's The Secret Seven meet Francis Urquhart.

The only pleasure to be derived from this farrago is the joy of reading a roman a clef, the pleasure of identification, however spurious and fanciful. The reader inspects the dim but intrepid figure of Joanna looking for signs of Ms Keays's cool hauteur, but finds none. Far more promising is the older figure of Laura, Joanna's cousin, a Commons veteran who is described thus: "Her eyebrows and lashes were dark, her eyes a greeny-grey, with a faint puckering of tiny creases at the corners and beneath the lower lids. The slight upward slant of her eyes, high rounded cheekbones and the little double crease at the corners of her mouth gave her the appearance of being on the brink of a smile". Thus we have the spectacle of a fictional Sara Keays regarding her younger self, the one who embarked on an affair with the dashing Cecil at 23.

Moving along, you note the resemblance of Ian Swift MP to Stephen Dorrell. Joanna's boss, Harry the Whip, is a dead ringer for John Patten. And as for his wife - "a smartly dressed, rather too-made-up woman with short, stylish blonde hair sprayed into immobility ... she had sharp blue eyes that showed just a little too much of the whites and gave her as slightly startled look" - Mrs Thatcher briefly waves at you from the page. But amid the meetings and scandals, the neglect of constituents and rumours of blackmail, one searches for Cecil in vain - among the MPs, that is.

Then a thought strikes you and you turn back to Chapter Two: "A man came in ... He was tall, immaculate in a dark suit, exuding self-confidence. His black hair was thick and glossy, his skin glowed with a ruddy tan". He is Randall Myers, a Commons researcher ("Good-looking, don't you think?" asks Laura, the fictional Older Sara). And you shout, "Cecil! At last!!". As Ms Keays's weary plot tacks to and fro, Randall darts and flickers through the pages, eavesdropping here, snooping in empty offices there, saying "I can see you're someone I'm going to want to get to know", in Clifford-the-dragon tones.

The characters don't like him, wonder if he's officially employed as a government spook, then forget about him for 50 pages. While the whips' office is in turmoil, the PM ruggedly decisive and Keays's heroine Jo in picturesque trouble, Randall/Cecil becomes a wholly marginal figure - a sort of Wandering Creep, forever condemned to the edge of the action, outflanked by American rivals and eventually found dead "in an isolated stretch of woodland". Revenge, of a sort, at last.