At the risk of playing straight into her hands, the question has to be posed: what was going through Sienna Miller’s mind when she popped on those support knickers for the party after the New York premiere of Factory Girl, in which she plays Andy Warhol’s muse Edie Sedgwick?

Was it a) these are just the ticket to make me look even more svelte and Sedgwick-like once I’ve slithered my way into that slinky black dress from Marchesa . . . lucky the weight stayed off . . . damn it, my legs look good. Ah, if Jude/Heath/Orlando could see me now . . . I wonder what Jude’s up to these days? I hope he’s not back with . . . ohmigod, I forgot to put the dress on. Crikey, what are they all staring at?

Was it b) OK, these knickers won’t go down well with British Vogue but they’ve already featured me twice. The Americans will think I’m a kooky Brit and invite me back on to Jay Leno; Grazia, Now and Closer will put me on their covers and the tabs will do something on how I’m a size 0, which should put another 0 on the end of my next cheque. Yoohoo, paps, I’m over here!

Or was it c) I am a serious actress. Clothes are no longer my priority. I do hope that going out in knickers and tights will finally confirm to everyone that I have very profound thoughts drifting through my mind and that I don’t even know that tight is the new volume and that the new Marc Jacobs shop opens in London in 11 days’ time. Why is everyone asking me about my knickers instead of my motivation?

Yesterday Miller said that she was “channelling” Edie Sedgwick, although so far no pictures of Sedgwick similarly dressed have been unearthed. Perhaps we should take Miller’s statement in the same spirit as her apparent hope that “all the films I’ve made this year will take the focus off what I’m wearing or my relationship”.

Given that the cinema reviews have been mixed, though, perhaps she has changed tactics and wants all the knickers she has worn this year to take the focus off her films.

Whether the knickers-and-tights combo was pure calculation (and only she has the answer), Miller’s outfit is the perfect cipher for our times: bad taste pushed to the point where it no longer defines anything other than an overweening desire for attention.

She is far from being the only celebrity (and would-be celebrity) to flirt with weird outfits.

Madonna tested the waters in 1991 when she wore a rhinestone Dolce & Gabbana corset and little else to Cannes. It was the first time that fetishism and fashion had been on a date together in public, and since Madonna had already carved herself something of a reputation as a performance artist, for a while it remained the last.

It was only when a little-known actress called Elizabeth Hurley wore a bunch of safety pins and some left-over black Versace fabric to the premiere of Four Weddings and a Funeral in 1994 and was catapulted into the mainstream that the potential finally manifested itself. Hurley’s impact was such — hugely lucrative careers as a model, actress, designer and Just Being Liz Hurley — that Wacky Outfit at a Premiere became an approved career-boosting ritual. Countless B, C and W-listers, including the inevitable former Big Brother contestants, have followed in her footsteps, each trampling on whatever was left of their self-respect but also carving out some profitable if short-lived niche. It’s all very entrepreneurial but the downside is that every time a nother red carpet is unfurled, our expectations are lowered (or, depending on your point of view, raised).

It takes considerable effort and ingenuity to secure headlines these days because we have all become adrenalin junkies. Hurley’s risqué Versace dress would no longer guarantee her a Sun front page. For a tabloid splash, an outfit cannot merely be bad or a bit tarty; it has to reveal some psychosis on the part of its benighted wearer — anorexia, tanorexia, spendaholicism, cheapaholicism, mutton-dressed-as lambism, lamb-dressed-as-hookerism. It almost goes without saying that the wearer will also be suffering from advanced stages of exhibitionism.

It’s hard not to sympathise. The longevity of reality TV — far greater than anyone predicted — has ensured that the world of celebrity is a very crowded place.

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