Last week I attended the Cannes film festival and since returning I have been trying to work out what the point of it is.

On the face of it, this isn’t a difficult question. It is an opportunity for filmmakers to sell the distribution rights to their projects in various foreign territories. To take just one example, that is why the producers of There Are Dark Forces, the documentary about the Diana inquest, decided to show a 20-minute extract from their unfinished film to a succession of journalists. They hoped that the previously unseen footage of Prince Philip in a Nazi uniform would provoke such an international outcry that the film would be snapped up by an American distributor.

But what of films like Blindness, the Fernando Meirelles-directed thriller that opened the official competition? That already has a full compliment of distributors so what was the point of bringing it to Cannes? Again, the answer is obvious. The filmmakers expect to pick up one of several prizes available at the festival in the hope of winning over the critics. When it comes to an independent film like Blindness, a good critical reaction is crucial to its box office success.

The mystery is why the makers of Indiana Jones and the Kingdom of the Crystal Skull decided to hold their world premier at Cannes. It was, by some margin, the most high-profile event of the festival, with a lavish party and a host of stars in attendance. What was the point of this three-ring circus? The latest addition to the Indiana Jones franchise certainly doesn’t need any help on the publicity front. Judging from the tracking -- the research that studios carry out to gauge the level of public awareness of their forthcoming films -- Paramount could neglect to spend a single penny on publicising Indiana Jones and it would still be the most successful film of the year. So why bother to open it at Cannes?

The answer, I suspect, is simply to boost the egos of George Lucas and Steven Spielberg. The film itself may not need any additional attention, but the film’s makers certainly do. The top executives at Paramount, the studio that is distributing the film in both the US and the UK, know that they have to make a big fuss over Lucas and Spielberg in order to keep them on side in case they want them to make a sequel. Throwing a party for them in Cannes is a small price to pay to secure their services.

And that, I think, is what Cannes is really about. It is an opportunity for famous producers and directors to bask in the spotlight, not because they need to in order to sell their films, but simply because they enjoy the attention.