In the six decades since Marlon Brando popularised the Rhythm Method (or whatever it was they called the acting style taught at Lee Strasberg's famous Actors Studio) we've been fooled into thinking that acting is all about becoming the person you're playing.

It isn't. Acting is actually just about dressing up.

As any child or superhero will tell you, the best way to become a person is to wear a costume – you don't need any of that Method nonsense. So look again: aren't thespians just big kids with a well-stocked wardrobe instead of little kids with a box of Mum's old dresses?

Sticking with Brando, there's only one rational explanation for his appearance as Jor-El in 1970s clunker Superman: the director promised he could wear a tinfoil cape and have a big "S" on his chest. Wouldn't you say yes? There are many other actors who have clearly based their career choices on what clobber they are going to get to wear and many others who are fastidious about costume choices. While filming The Untouchables, for instance, Robert De Niro stipulated that he be given silk underwear in which to house his unmentionables so that his character – Al Capone – had the right "swish" to his walk, or whatever it is silk underwear adds to your gait.

Likewise many actors have been defined by the clothes they've worn on screen. Conjure up a mental image of John Travolta and, unless you're one of the weird few who see him in a butch flying jacket in the Breitling ad, you'll picture a man in a white suit (Saturday Night Fever) or a man in a black suit (Pulp Fiction).

As luck would have it, the first of those suits is one of the main attractions in Hollywood Costume, an exhibition of 130 famous film outfits drawn from private collections which opens at the Victoria and Albert Museum in London next weekend. The show is co-curated by Deborah Nadoolman Landis, professor of costume design at (where else?) UCLA and the woman behind the iconic screen costumes worn by Harrison Ford in Raiders Of The Lost Ark, and Dan Akroyd and John Belushi in The Blues Brothers. She also worked on Michael Jackson's Thriller video, directed, like The Blues Brothers, by her husband John Landis. It was her detective work which helped uncover the Travolta suit: last seen in the mid 1990s when it was sold at auction for £93,000, it was eventually run to ground in London after an international appeal.

The white three-piece is made of "completely gross polyester", Nadoolman Landis has said, and was bought off-the-peg in Brooklyn. It has a 28in waist which means, while I love dressing up as much as the next RADA graduate, I'd need to be Superman to get it over my thighs.

Guess I'll have to stick to Mum's old dresses. n