I'm not celebrating anyone's birthday (best wishes if it's yours), but those books, films and television programmes you can read or watch time and time again.
    There are now TV channels that repeat series on a rolling basis. As soon as they come to the end, they begin again. I suppose people find them comforting in a way, much as the shipping forecast is. They offer a kind of stability. It's comforting to know that somewhere on the television there'll always be an episode of Midsomer Murders. But does this make them classics? At Christmas and other bank holidays people can look forward to repeats of Morecambe and Wise, The Great Escape and It's a Wonderful Life. There isn't necessarily anything seasonal in their content, but watching them has become a tradition.
    For many people, me included, it's books that they return to regularly. They might describe ways of life that no longer exist or that never existed, they might be personal favourites or have a mass following, so what makes a classic? Why don't some works date or lose their magic? Is it a matter of engaging actors, good directors or atmospheric sets? If it was only that, the Star Wars prequels wouldn't have faded so quickly.
    Classics bring together memorable characters that people can recognise even if they don't identify with them. They can be grotesque or sympathetic, but it must be possible to imagine them having a life outside the story. The story itself, no matter whether it's elves, aliens or kitchen sink drama, must also transcend the characters and speck about the human condition, giving the characters recognisable dilemmas or placing them in situations where you wonder what you would have done. Beyond this there's a sprinkling of fairy dust, some indefinable magic. It's great when it happens, but no one can really predict it, which makes the job of agents, publishers and programme commissioners such a gamble.
    I'd love to write a classic, but meanwhile I'll settle for writing about someone else's. My essay on Dorothy Richardson's short stories is now available on Thresholds at http://blogs.chi.ac.uk/shortstoryforum.