A great sex scene in a novel is like happiness.  When you see it, you know.

But it’s not easy to nail. The Literary Review’s Bad Sex in Fiction award – rightly feted at the In and Out Club in London – was launched in 1993. Infrared’s author Nancy Huston scoped the prize in 2012 with unforgettable imagery like “my sex swimming like a fish in water”. I’m guessing it gets harpooned later.

Mounting often features in sex scenes but Rowan Somerville tweaked the cliché: “like a lepidopterist mounting a tough-skinned insect with a too-blunt pin he screwed himself into her”. As Somerville said when accepting the award, there’s nothing more English than bad sex.

Just choosing the words is a challenge. Will they be biologically correct, or do you prefer words you don’t want the kids to repeat? Maybe there’ll be some common metaphors, or fancy phrases like Ben Masters’ ‘elfin grot’. Some writers shoehorn in some long words like anaconda, rissorgimento and philately. It makes readers think they’re erudite, or at least that they own a dictionary.

One of my favourite writers is Penelope Lively who does unresolved sexual tension better than anyone I know. Now and then we still get to go all the way. Bliss. Instead of using the whole thesaurus, she uses all the senses, as in The Photograph.

He spreads his coat on the grass, puts her down on it. She kicks off her trousers. It is the most urgent sex he can ever remember, a glorious immediacy, pinned forever in that place – the wind, the smell of crushed grass, some small piping bird, sheep moving about.

Lively doesn’t need to say that the grass is scratchy on the skin.  Why else would Glyn put his coat down?

Not all readers are after the same thing. Sometimes raw and raunchy fit the bill perfectly, as in Mel Sherratt’s Taunting the Dead.

She ran the tip of her tongue up and down his shaft as he held her head in place. Might as well get it over with and then she could be on her way.

Maggie O’Farrell’s After You’d Gone has this study of Alice losing her virginity.

She begins counting the punching thrusts to try to block out the consciousness of this heaving, panting body thrashing about on top of hers. At number seventy-eight, she feels his back arch and at seventy-nine, he does a kind of prolonged rigid shudder and collapses on to her, breathing hard.

That was infinitely sad. For making sex funny, you have to hand it to Howard Jacobson. Here’s a passage from Coming from Behind.

Now that his gown has ridden up his back and hangs over his face, he is as blind as a school photographer, and it is his other end anyway… which confronts the door.

For me, there’s one criterion above all that’s the hallmark of a good sex scene. It’s the one I use in my fiction, and it’s simply this: when you read about the characters having it off, does it turn you on?

I’d love to hear what you look for in a fictional sex scene and who your favourite authors are.