So, it's happening again: people are stealing my ideas. It was the same when those two films about Columbus came out in 1992, forcing me to abandon my long-cherished screenplay, in which I focus exclusively on the explorer's childhood, and, in particular, his relationship with an imaginary friend, Stoffard (a brilliant plot device of my own invention).

Someone suggested that perhaps those other films were motivated by the then current 500th anniversary of Columbus 's voyage in 1492, but that seems pretty tenuous to me. And there are no anniversaries to explain the recent rash of sword-and-sandals films set in the ancient world that have all been ripped off from an idea I've been working on for the last six years.

Admittedly, my story focuses on Pythagoras, and the earth-shattering effect of his theorem that the square on the hypotenuse of a right-angled triangle is equal to the sum of the squares on the other two sides, while most of the recent films about Troy, Sparta, Alexander, and so on, have tended to feature thousands of warriors with hugely muscled thighs and streaked hair engaging in spectacular, CGI-enhanced epic battles, but it's obvious that, basically, they stole my idea.

This kind of thing goes on all the time, and it's completely brazen. If you send an unsolicited script to a major broadcaster, they virtually admit that they're going to steal it.

They send you a letter that says, in effect, "Look, if we reject your script, and then, nine months from now, you see a programme that's a bit similar to your idea, it's simply because we were already developing something along those lines, okay? Now, sign here, and please don't turn out to be one of those nutters who's going to give us a hard time." Well, I'm not falling for that.

How can I protect my ideas?

But how can you protect your ideas from plagiarism? Some people suggest sending yourself a copy of your script or treatment by registered mail. But just think about it for a moment: how many hands will your manuscript pass through on its journey through the postal system? Statistically, it's almost a dead certainty that one of those people is an aspiring writer. No, far too risky.

So, even though I take every possible precaution, how, exactly, are these people managing to steal my ideas? After much thought, I've realised that there's only one rational answer. All the major broadcasters and film makers are employing teams of highly trained psychics and telepaths to follow me around and read my mind.

Now, you may quibble with the use of the word 'rational' in this context. And, to be fair, so did my doctor. Especially when I showed up wearing my patented anti-mind-probe device, which is a large, pyramid-shaped hat that covers my entire head and is lined with alternating layers of tin foil, lead, and goose fat. Yes, it draws some quizzical glances in Tesco, but it does have the added advantage of being waterproof.

During the consultation, my doctor asked what kind of ideas I imagined were being stolen from me. I told him it wasn't imagination: the facts were staring him in the face. So was I, and he asked me to stop as he found it disturbing and my breath was steaming up his glasses. It was only later that I got suspicious. Why did he want to know about my ideas? I realised that he was part of the conspiracy.

Sure enough, as I entered his surgery on my next visit, he was hastily concealing what was unmistakeably a screenplay. It was disguised in the binding of a medical text book on mental health, but the size and shape were a give-away to the trained eye. He tried to deny my accusation, but his protestations were so hysterical as to be almost incoherent. Even when I let go of his throat and he could speak properly he didn't begin to convince me.

At that point, I took the only available option to protect the integrity and copyright of my exclusive material. I don't know if you've ever held a doctor hostage in his own surgery, but the great advantage of the location is the availability of interesting medication.

After the third day of the siege, I began to see things in a different light. So did the doctor, as I was forcing him to test the various pharmaceuticals on himself before I sampled them. Suddenly, I realised that the doctor was, in fact, my best friend - which he proved as soon as I gave myself up, by arranging for me to be granted access to a safe, secure environment in which to develop my ideas. The walls contain a special type of padding that's impervious to the mind-probes of the telepaths, whom I can hear, day and night, muttering in frustration, just the other side of the walls. So, now I can write my story.

It's about someone who is convinced that his ideas are being stolen by people reading his mind. At first, everyone dismisses him as a paranoid lunatic, but in the end it turns out to be true; he's vindicated triumphantly, turns the story into a blockbusting movie, and becomes the boss of a major film studio.

That's my idea. And I'm not worried that I've just revealed it to you. Because if you try to steal it, you'll find that strange things will start happening to you. You'll begin to have the uneasy feeling that someone is stealing your ideas. And it'll be me. I'm doing it now. Every day, I hear more and more voices in my head. And those voices are your ideas.

But now they're not yours any more, they're mine. Mine! You hear? ALL MINE!

Paul Bassett Davies is a Euroscript tutor and director.