The thing is that the idea that Shakespeare didn't write the plays attributed to him is one of history's stupider conspiracy theories. You can tell, because the new film espousing this theory, Anonymous, is directed by Roland Emmerich, who wrote and directed the abysmal 1998 movie, Godzilla, and also The Day After Tomorrow, a film whose tension peaks when Jake Gyllenhall is pursued by the weather getting a bit parky.

And you could tell, even before the movie, because it's a classic argument from no evidence, which invariably makes for bad history. The Shakespeare-doubters love evidence-that-isn't-evidence. So Shakespeare can't have written the plays, goes their argument, because he doesn't mention them in his will, and if he'd written them, he would obviously have said something.

But this disregards everything else Shakespeare didn't mention in his will. His most famous bequest is his second-best bed, which he left to his wife, Anne Hathaway. Nowhere in his will does he mention his first-best bed: so, following the logic of the doubters, presumably he didn't have one of those either. I guess if he didn't write Hamlet, he didn't need a nice sleep after finishing it.

He also can't have written the plays because many of them are set in foreign countries, and Shakespeare wasn't widely travelled. So thank goodness no one tried to reconstruct the authorship of The Tenderness of Wolves, the 2006 Costa-Award winning novel set in the snowy wastes of Canada in 1867. Its author, Stef Penney, had never been to Canada. She'd never been to 1867, either. Perhaps Shakespeare, like Penney, used imagination instead.

The third reason why Shakespeare can't be the author of his plays is because he died several years after the last one was written, and it's inconceivable that he might have had a couple of years off. Imagine the conspiracy theories which will one day surround Harper Lee, who wrote her first and last book 51 years ago, and is still alive today.

The anti-Shakespeare sentiment which permeates Anonymous is nothing more than class and regional prejudice. The arguments for Shakespeare not writing his plays eventually boil down to the idea that an ordinary bloke from the Midlands couldn't have written anything beautiful. It's more plausible, in the film, that Edward De Vere wrote them, even though he died nine years before the last Shakespeare play was written. Being the Earl of Oxford is apparently more important than being alive, in terms of creative genius.

The Shakespeare Birthplace Trust is taping over Shakespeare's name on roadsigns this week to draw attention to the fact that people keep trying to erase him from history. They shouldn't worry: Shakespeare will assuredly survive Roland Emmerich. Even if Godzilla didn't.

n.haynes@independent.co.uk