The Birthday Present by Barbara Vine

He hasn't broken the law — but his political life depends on his not being linked to the dead woman. You keep wondering what he'll do to stop the secret from getting out. Like the best Barbara Vine books, it's sinister, exciting and beautifully crafted, like a fine piece of watchmaking.

Synopsis from Foyles.co.uk

Mention his name and most people will say, 'Who?' while the rest think for a bit and ask if he wasn't the one who got involved in all that sleaze back whenever it was ...? It's late spring of 1990 and a love affair is flourishing: between Ivor Tesham, a thirty-three year old rising star of Margaret Thatcher's Conservative government, and Hebe Furnal, a stunning North London housewife stuck in a dull marriage. What excitement Hebe lacks at home, however, is amply compensated for by the well-bred and intensely attractive Tesham - an ardent womanizer and ambitious politican. On the eve of her twenty-eighth birthday, Tesham decides to give Hebe a present to remember: something far more memorable than, say, the costly string of pearls he's already lavished upon her. Involving a fashionable new practice known as 'adventure sex', a man arranges for his unsuspecting but otherwise willing girlfriend to be snatched from the street, bound and gagged, and delivered to him at a mutually agreed venue...Set amidst an age of IRA bombings, the first Gulf War, and sleazy politics, "The Birthday Present" is the gripping story of a fall from grace, and of a man who carries within him all the hypocrisy, greed and self-obsession of a troubled era.