Every scene has a Silva lining

The costume designer of Unsuspecting Susan thanks heaven for Velcro fastenings

Even the simplest of theatrical productions needs a costume designer. For Claudia Silva, whose undertaking it is to dress Celia Imrie in Stewart Permutt's solo piece about a privileged, protected woman (Susan Chester) whose son commits a shocking crime, the relevance of the character's wardrobe is especially pertinent.

Set in one room, and taking place over the course of a year, Imrie's clothing will help convey to the audience the vital subtleties of change in her character's mood and development, while also underlining seasonal shifts in the world outside (although Imrie holds the stage alone, many of her monologues take place over the course of several months). Armed with only words to propel her character's psychological trajectory, Imrie's wardrobe will be a particularly useful prop in helping the audience understand who Susan is.

Already well-recognised for her performances in Victoria Wood's television sketches, as Robbie Coltrane's wife in The Plan Man, and a theatrical career in which she has been as comfortable handling Pinter as she has Shakespeare, audiences will expect a tour de force performance from Imrie in Unsuspecting Susan. Based on the story of a busy working mother and actress who is forced to confront her son's wrongdoing, it sees Imrie tracing a path from naivety to cynicism. She starts as an innocent, casually recounting whimsical anecdotes and petty scandals about her friends and neighbours. It is only later, when the truth about the crime becomes public, that her tone and personality have to become darker for her to survive.

"Think middle class, mother, Home Counties, court shoes, mid-calf skirts and cardigans," says Claudia Silva, when describing the characteristics that informed her choices for Imrie's wardrobe, before pointing out the practicalities of trying to fit several costume changes into a one-woman show without an interval. "There are seven scenes and seven outfit changes. Some subtle, some less so. Sometimes she has to rush off and slip on a little black number, or her pyjamas," she says. "But it's quick. The clothes have Velcro buttons so Celia can rip off layers to reveal a costume change underneath – in one change she might simply take off a cardigan to reveal a blouse."

Silva sourced most of the costume from charity shops in west London, but she is quick to acknowledge that Imrie also had strong instincts about how her character might present herself. And, while Silva concedes that such strong personal ideas from those involved "can make designing more difficult for me", she also admits to enjoying the experience of working "more closely with the actors. It's more interesting that way."

Unsuspecting Susan, King's Head Theatre Club, 115 Upper Street, London N1 (020-7226 1916; www.kings headtheatre.org) Mon to 15 Jun, Tue-Sat 8pm, mats Sat & Sun 3.30pm, £17.50/£15.50/ £12 concs