If you see the new film Cloclo, a biopic of the singer-songerwriter Claude François (which I review in tomorrow's edition of the NS), do keep an eye out for the 38-year-old actor Benoît Magimel, the pretty-boy star of The Girl Cut in Two, The Piano Teacher and Little White Lies.

I didn’t. Having spotted his name among the cast list, his participation in the movie slipped my mind entirely until a friend and I were discussing Cloclo a few days ago. Benoît Magimel, of course! I forgot he was even in it - remind me which part he played again? But then it’s hardly surprising I overlooked him when he bears about as much resemblance in the film to his real self as Justin Bieber does to Ernest Borgnine. You can see for yourself here the disparity between the perfectly fetching Magimel as he usually appears, and the intimidating, breeze-block-faced Cloclo version. I’m sure you will agree that, while not quite analogous to Gary Oldman in Hannibal, this is no mere case of Kidman’s Nose.

It’s not hard to fathom why the film’s director asked Magimel to undergo this prosthetic overhaul, or why the actor agreed. He’s a fine performer, and very strong in the part of François’s manager Paul Lederman, but disguise adds another layer to the work. It’s a tradition that can pay dividends come awards season - think of Charlize Theron in Monster, Robert De Niro in at least a third of Raging Bull or, yes, Nicole Kidman in The Hours - but it would be cynical to suggest that this influences those performers’ decision to go at least partly undercover.

Being in the glare of attention, whether it’s from the camera, the public or the paparazzi, must leave performers thirsty for a get-away-from-it-all break from themselves. Doing that on screen has its own perverse glint - you are there, and yet not there. This can be expressed in the form of in-joke (Cate Blanchett appearing behind a mask in Hot Fuzz), eccentricity (Debra Winger as a male angel in Alan Rudolph’s strange, forgotten 1987 film Made in Heaven) or in a film’s entire casting approach (James Caan, Dustin Hoffman and Al Pacino “uglied up” as the villains and miscreants of Dick Tracy).

Disfigurement and disability necessitates the adoption of prosthetic disguise or concealment: the likes of Charles Laughton in The Hunchback of Notre Dame, Eric Stoltz in Mask and John Hurt in The Elephant Man had little alternative to submerging themselves in make-up. (Though some tantalising clips survive of David Bowie playing John Merrick without any cosmetic assistance in a Broadway production of The Elephant Man; the role was also taken at various points by Bruce Davison and Mark Hamill.) And a grimace or an ill-tempered sneer is never going to be enough to pass as monstrous in fantasy cinema: Tim Curry’s glazed scarlet body, clomping hooves and potent ebony horns in Legend are impressive even in our CGI-dominated age, not least because they represented such a violent reaction against the same actor’s camp showbiz persona honed in the likes of The Rocky Horror Picture Show and Annie.

CGI and motion-capture now enable every actor to inhabit their own performance in animated form. (A blue bodysuit peppered with dots, each one corresponding to a different joint, allows the actor’s movements to be replicated by a computer-generated equivalent: think of the performer as a puppeteer operating a million strings on a marionette that, in turn, resembles a monstrous likeness of him- or herself.) So we can know we are watching Daniel Craig, Jamie Bell and Andy Serkis in The Adventures of TinTin: The Secret of the Unicorn, or Willem Dafoe in John Carter, without actually clapping eyes on their flesh-and-blood forms. (Then again, cinema is only light on a wall, so any discussion of degrees of physical authenticity must be moot.) Serkis in particular has made a career out of giving performances in CGI disguise: how many of the billions of people who have admired his work in King Kong, Rise of the Planet of the Apes and the Lord of the Rings trilogy would have recognised him had he not enjoyed a few moments of non-CGI screen time in the final LOTR instalment, The Return of the King?

Kevin Spacey reflected on the art of staying hidden back in 1997:

Paul Bowles thought of himself as a spy. A secret agent. He said his job was to get information across the border. I very much feel that way as an actor. You can accomplish that task as long as you remain a spy. When you're uncovered, you can no longer move quite as stealthy, you can no longer dodge the radar. I've always chosen to let the work speak for itself. I like to stay in the shadows.

He was talking about his reluctance to discuss his private life, but the same principle surely feeds into the disguises actors adopt. It’s not just the ostentatious shrugging off of vanity, the relinquishing of that side of the actorly persona which demands photo approval or a stylist on 24-hour call. Putting yourself beyond even the basic recognition factor for audiences allows the performance to be seen without baggage or associations - to dodge the radar, to use Spacey’s metaphor.

Of course, a good actor will either do that anyway, or use the baggage of past roles to their advantage. Anonymity, though, opens up a new sort of freedom. If these secret agents could only learn to let go of the on-screen credit and go unbilled, the experiment would be complete and extreme. Imagine that: an entire film in which an A-list cast remains stubbornly unidentifiable and uncredited. There’s something delicious about that idea, even if it does require a basic subscription to the cult of celebrity in order to make effective any advertised retreat from it. But if fame is a mask that eats the wearer’s face, maybe this is the only avoidance tactic available to the celebrity performer short of retirement: the mask that masks the mask.