As you might have noticed, there’s a tremendous rage on at the moment for screen adaptations of classic texts. I have been one of the principal beneficiaries of this trend. I’ve done Middlemarch and Pride and Prejudice, Moll Flanders is in post-production and will be ready for screening in September, Emma is being filmed and will be shown on ITV at Christmas, and I’ve completed the screenplay for Daniel Deronda. Jane Eyre and The Mill on the Floss, however, have been snatched from my slavering jaws, and The Tenant of Wildfell Hall is ready to go on BBC2, again adapted by somebody else.

You would think that I’d be glad when someone else takes these mighty tomes on: not a bit of it. I get quite miffed. Especially when they give Sense and Sensibility to Emma Thompson. I mean, that’s not fair, is it? It isn’t as if I demanded to play the female lead in Howards End.

There are all sorts of questions that people ask about adaptation. Isn’t it terribly difficult to translate from one medium into another? How can you be true to the author’s original intentions? How can you be true to the period and yet speak to a modern audience?

Basically these can all be reduced to one simple fact: every reading of a book is an adaptation. There are as many Middlemarches (or whatever) as there are readers.

And as we read, we’re screening our own adaptations in our mind’s eye. Making our own pictures of the hero and the heroine, hearing their voices, seeing the settings, even feeling the air and the grass under our feet. Consciously or unconsciously, we’re interpreting, choosing which aspects of the story to foreground or to set aside.

With very widely read books like Pride and Prejudice, we have the opportunity to join in the great conversation, to compare our individual adaptations, to see whether we imagine the characters in the same way as other readers. Some participants in the conversation are privileged: they write books or give lectures or teach classes on Jane Austen. I used to do that for a living in schools and at Warwick University. Trying to turn other people on to my vision, my reading of Emma, or whatever.

Now I have an even more privileged standpoint: I can offer my interpretation to millions and I have access to lots of talented people and lots of technology to get that interpretation on the screen. (Though, of course, by the time it reaches the screen it’s been re-interpreted by the director, the actors, the designers and the camera crew.) Setting about the task of adaptation is different with every book, but it is possible to make a broad division between extremes.

If I’m adapting something like Emma, I’m offering a reading of the book which may be personal, but is always faithful - that is, I can justify everything I do in terms of the book itself. I may invent some scenes, but they are implied by the book. I’m not trying to improve on it but to lay its essence bare to a modern audience in as visual a way as I can.

If I can take Emma for a moment - I was very interested in Austen’s remark that the heroine is someone whom “no one but myself will much like”. You can say that again, Jane. I don’t like Emma much for a start - she’s fearfully snobbish, she has a lethal combination of arrogance and ignorance, she’s curiously asexual, she’s a bully, and she treats people like puppets.

So why did Austen like her? Because she has the imagination of an artist. She takes the lives around her and weaves them into patterns based on her own wishful fantasies.

Unlike a real novelist, she writes her fictions not with characters but with real people. So I thought - let’s see Emma’s fantasies on screen. Her imagination leaps forward to see the marriage of Elton and Harriet, with Elton expressing eternal gratitude to Emma for finding him such a lovely bride, and Harriet saying “and to think I should turn out to be the daughter of a Baronet!” The other kind of adaptation could be called asset-stripping - the producer has bought the book not because it’s great, but because certain aspects appeal and can be built upon. Perhaps just the central character, perhaps the basic premise of the plot.

In Wilderness, for example, (a story about a female werewolf to be shown on ITV this autumn) we transposed the setting from Los Angeles and Canada to London and Scotland, junked all the dialogue and half of the characters, and changed the ending. When you do this sort of thing it’s a bit like writing the story you wish the novel had been but wasn’t - I think most readers will recognise this feeling.

By now (I hope) you will all be thinking “this sounds like fun - how do I get in on it?” The grim truth is that you probably don’t.

These big classic adaptations are generally regarded as perks for the heavy mob, rewards for long and reliable service in the field.

Even if you discover some long-hidden or long-neglected masterpiece, and submit a brilliant treatment for it, they’ll probably say “Oh thank you so much for bringing this to our attention - I think we’ll ask Andrew to have a crack at the screenplay.”

There are exceptions. It helps it you’re an internationally known actress, of course, but David Nokes came from nowhere (university teaching, actually) with Clarissa and now the soon-to-be-seen Tenant. So it can be done.

But there are some other ploys I would like to suggest. First of all, for those of you who see yourselves as teachers and facilitators rather than screenwriters: adaptation as a way of bringing the text alive for your students. This is something I used to do a lot when I was a teacher.

Devise a title sequence for The Rainbow that not only expresses the earthiness and aspiration of those early pages, but also suggests the theme of the whole book.

And your adaptation doesn’t have to be for screen: when I was teaching dance students English I used to get them to devise dances which would express the structure of the novel we were studying.

When I had a group who couldn’t get on with Mrs Dalloway, I assigned them all characters from the book, and got them to write brief monologues for their character, which we assembled into a sort of radio play.

My other great suggestion is the Free Imaginative Interpretation. Many of us find that the hardest thing of all is thinking up a good story.

The answer to this is: why do you feel you have to have an original story? Shakespeare never let that bother him, after all. He just raided the classics and history. So why not do the same?

If we can take Emma yet again (sorry about this, but it’s so recent I can’t get it off my mind) we’ve already had a free adaptation of Emma this year in Clueless, Amy Heckerling’s film that sets the Emma story in an affluent LA high school.

As in Jane Austen’s novel, the airhead heroine starts off by irritating the hell out of you, but by the end, you kinda care about her. It also contains a brilliant line from the Harriet figure: “I don’t know why I ever listened to a virgin, who can’t even drive!” Which says a lot about the original Emma, too, I think.

But that by no means exhausts the Emma possibilities. Think what Tennessee Williams would have made of it. Emma, that exotic bloom, alone in her vast mansion. Her father, like a little old white grub, trying to suck the life out of her, warming himself at her flame.

Down the road, in his own mansion, Mr Knightley has been lusting for her since she was 10 years old. “Ol’ Mistah Knightley, he sho’ like little Emma!” say the black mammies chuckling acutely. Not until it’s too late do we realise what we should have known all along: that Mr Knightley is, of course, Emma’s natural father.

Less perversely: how about a modern Sense and Sensibility? Two girls, not necessarily sisters, but deep and true friends. One of them falls in love recklessly, self-destructively, cataclysmically.

The other feels almost as deeply, perhaps just as deeply, but is constrained by caution, rationality, or perhaps fear of her own power to hurt. We love and care about both of them. We long for a happy outcome - but how can that happen, in the world as it is?

I feel enormously tempted to have a go at that last one myself, but in an uncharacteristic mode of generosity, I’ll make you a present of it. One piece of advice: take it to the limit. And enjoy yourselves!

Next week A masterclass from Richard Stilgoe on musicals