Every so often there comes a film so excruciating, you find yourself worrying that you are in a real-life Truman Show and the rest of the world is watching you from behind the cinema screen and laughing at you as you sit through it. Diana is one of those films.

The new biopic about Princess Diana and specifically about her love affair with the heart surgeon Dr Hasnat Khan, premiered on Thursday and is released in two weeks. It is 113 minutes long. You can do a lot in 113 minutes – defrost a freezer, drive around the M25, watch William & Kate the TV drama one-and-half times. All of these, arguably, would be more edifying and enjoyable than sitting through Diana.

It was never going to be Citizen Kane but on paper the film looked like it might just work. It is made by Oliver Hirschbiegel, Oscar-nominated director of Downfall, about Hitler’s last days. It stars Naomi Watts and Naveen Andrews and has a class supporting cast including Juliet Stevenson, Geraldine James, and Douglas Hodge as Paul Burrell.

Unfortunately it also has a leaden script which sees Diana asking her surgeon lover questions like, “How long does a heart operation go on?” (Baffling answer: “You do not perform the operation. The operation performs you”) and, coquettishly, “So… hearts can’t actually be broken?” Meanwhile improbable scene follows impossible scenario – Di disguised in a wig being wolf-whistled by every man she passes - on Old Compton Street; Di wandering alone, tights ripped, through a deserted night-time London; Di and Hasnat driving to the cliffs of Dover for no clear reason except to tee up a smoochy montage soundtracked by “Ne me quitte pas.”

That last bit, by the way, Hirschbiegel just made up. “They never did that”, he said. “But I felt I needed to show… how much they enjoy each other.” Director’s licence is fine but what if your subject is still so world-famous that she, or even a Hollywood incarnation of her, can make emotive front page news 16 years after death? And what if many of those closest to that subject are still alive? The question, though, is not whether it is too soon to make a film about Diana’s death. It is certainly too soon to make a bad film about it.

The question is what the motivations - barring the obvious financial ones - for making the film are. As an attempt to get under the skin of the “real” Diana, it fails miserably. Indeed, with its focus on fashion, soupy, half-imagined romance and glamorous sensationalism, it looks suspiciously like a live version of the front pages that hounded Diana in life – only in sharper focus and with added clunky dialogue. No-one needs to see that.

Yawning towards success

Three cheers for Simon Cowell. Not often one gets to say that but this week the multimillionaire mogul did a great thing for an undervalued member of society – the night owl. In an interview with Esquire, Cowell said: “I think being creative in the morning is virtually impossible. I’ve never had a good idea in the morning. That’s why I wake up about 11am.”

Now, haters of Il Divo, One Direction and television talent shows might argue that Cowell has never had a good idea after 11am either but superyachts and super straight teeth do not buy themselves so it is conceivable that he knows what he is talking about. And on this topic, he is quite right. It is barbarism to be expected to come up with anything of note before 11am – that is why newspapers don’t get cracking until mid-morning and get more frenzied and focussed as the night draws in. Many times I have tried to explain this to friends who are teachers, lawyers, etc. - responsible types with responsible jobs who leave the house before The Jeremy Kyle Show starts. They just narrow their wide-awake eyes and murmur something about Thatcher surviving on four hours a night.

Now I can tell them that it’s a creative thing. There is just one difference. While we imaginative late-risers are sprawled beneath the duvet, waiting for inspiration to strike before we can think about earning a crust, Cowell could very well never get out of bed again and still make enough off Harry Styles and co. to buy a new yacht every week. Sweet dreams.