Alison Jackson: The 'Big Brother' bosses had their claws out for Galloway

Not even I, someone with a special interest in fiction and reality, would have created an image of George Galloway on all fours pretending to be a cat feeding from an imaginary bowl in Rula Lenska's hands. Yet this is what viewers saw last week on Celebrity Big Brother. And can you imagine the self-righteous vitriol the Hon Member for Bethnal Green and Bow would have dealt out to anyone who had dared to satirise him doing such a thing?

But pay a man a few pounds to appear on Big Brother and there appears no limit to what he will do. We certainly shouldn't have any sympathy for him: if you sup at Big Brother's table, the one certainty is you will be given some unpleasant meals to digest.

There are, though, some intriguing questions. Did Mr Galloway know that he would have to perform this task? Was he even contractually obliged to do so? Channel 4 says not: that it was merely "a suggestion".

Was the publicity an unexpected bonus for the producers or a calculated attempt to get the programme splashed over the front pages of the serious press ­ a temptation that some papers, particularly one that recently confronted Mr Galloway in the courts, succumbed to with great relish?

Of course, we will never know. The creators of Big Brother are extraordinarily skilful at making it almost impossible for viewers to distinguish between what is real and what isn't.

The show presents itself as reality TV. But the truth is that it is a film set with carefully chosen characters who are obliged to perform in a confined yet very public space. There may be no formal script, but that does not mean it has not been created, written and edited. It is presented to the public as a slice of unmediated reality ­ in fact, it is a film in which fiction and reality have been blended in a deliberate, calculated way. Make no mistake. These people are very clever.

The programme is a quintessential expression of celebrity. To be a celebrity today you have to make public what is essentially private. But there is something rather suspect about the authenticity of the private because there is an agenda, a desperate desire for fame. Of course it is hyped up; it's a live soap opera, with all the larger than life melodrama manufactured as a private moment, the behind closed doors extravaganza that is now the essential ingredient of "reality" programming.

Those in whom we put our trust, who carry responsibility in some way ­ such as MPs ­ should respect the traditional boundaries between the public and the private. Tony Blair discovered this when he came out of No 10 after Leo's birth in his casual wear and tea mug with family picture ­ we didn't buy it. Yet the selling process isn't as anarchic as the Z-list celebrities, where anything goes. This is where George Galloway has got it wrong: Blair's image is carefully created and Galloway underestimates the importance of the constructed image today.

Amid this mêlée of truth and fiction, the image of Mr Galloway on all fours is a reality of its own, something we have seen with our own eyes. It has spawned a hyper-reality, a transient hysteria braying for his resignation that may bring about the demise of his career in politics

If this farce does end his stint at Westminster, we may not have much sympathy for him. But we also should question the means Big Brother has used to bring about his humiliation. If they get away with it this time, what will they think up for next year?

Myth, image, lookalike: it's all in your mind

I am sometimes asked about how my TV lookalike programmes are put together. Well, they are rarely straightforward. The setting up of these scenes is a major undertaking. Curiously, some of the lookalikes don't look that like the subject, but you see something in them that could, with the help of make-up, wigs and prosthetics. The man I used for Dodi al-Fayed was about 16 stone, much larger than the real Dodi. A black background made him slimmer and, as he was bald, I painted on his hair and blacked out his double chin.

We have to ask some "lookalikes" who they think they are. One man claimed his eyes were just like Diana's and went on to practise "the look"! Whoever he looked like, it was not the Princess of Wales.

With one lookalike of a film star, a girl came up at the end of a day's filming and asked to sit with him. I left for a moment and on returning found the room full of girls who had all taken their tops off.

When I was shooting a naked lookalike Camilla Parker Bowles being painted by a lookalike Prince of Wales in a garden, the place was nearly closed down in a furore as the staff said I would be upsetting the real Prince Charles. Similarly, when I was shooting a streaker running around the lookalike Queen, the location people had a fit.

It is the power of the image that fascinates me. When the country mourned the death of Diana, most of them were mourning a person they knew through images alone. The image of Diana seemed more real than the actual person.

All my work is about myths created through images. It simply isn't true that the camera doesn't lie.

Tony Blair Rock Star is on Channel 4 on Thursday

Janet Street-Porter is away