The folk behind this already notorious life of Saint Diana – she who walked through minefields for our sins – should be thoroughly ashamed of themselves. If you are going to offer us something this abysmal, then you really have a duty to make it properly hilarious. We demand mid-ranking telly actors doing poor impersonations of senior royals. I like the idea of Leslie Grantham as the Duke of Edinburgh. "Hello, I'm Prince Philip. These Chinamen really are frightful. Aren't they?" And so forth.
Sadly, none of that goes on. The leaden script focuses almost exclusively on a strikingly uneventful affair between two boring non-entities. One is a softly spoken Pakistani heart surgeon named Hasnat Kahn. The other is a characterless middle-class woman named Diana. It involves only mild hyperbole to argue that, had we not seen the poster, we'd find it hard to guess that Naomi Watts was playing the late Princess of Wales. Too short, too compact and not sufficiently posh, she comes across more like Tina Brown recovering from a recent general anaesthetic.
None of that would matter much if – like, say, Anthony Hopkins in Nixon – Watts managed to create a pseudo-fictional character that breathed its own imaginary air. Sadly, the wretched dialogue permits no such alchemy. "So hearts can't actually be broken?" she asks poor Dr Kahn at one point. Naveen Andrews, whose performance as the surgeon is remarkable only for its lethargy, does a very good job of keeping his face straight while replying.
Diana doesn't entirely avoid unintentional humour. Lines such as that may help it to gain some cult traction. There are more. "Nuclear submarine?" she says after being asked to launch such a vessel. "But I want to help people." A romantic montage to Jacques Brel's Ne Me Quitte Pas wouldn't be out of place in a Naked Gun movie.
Equally amusing is the film’s willingness to accept the absurd myth perpetrated after the Princess’s death that, rather than being a socialite who occasionally did a little charity work, she was an enemy of the state who spent every spare second feeding the poor and helping the lame to walk.
Most of the film – which suggests that director Oliver Hirschbiegel got really lucky with Downfall – is, however, too stupefyingly dull to compete with Mommie Dearest on the midnight movie circuit. Couldn't they have got Matt Lucas to play Elton John? Very poor.