Blake, who for the last four years has been playing the role of Beverley Unwin in "Coronation Street," will take over from Miriam Margolyes as the haughty school head mistress on April 2.

Blake's stage credits include Noises Off and High Society.

The London version of the hit Broadway musical, which has received four Olivier Award nominations, opened at the Apollo Victoria on Sept. 7, 2006. British actress Kerry Ellis took over from Idina Menzel in the starring role of the green-skinned witch on Jan. 1.

Wicked features a score by Stephen Schwartz and a book by Winnie Holzman. The creative team also includes scenic design by Eugene Lee, costume design by Susan Hilferty, lighting design by Kenneth Posner, sound design by Tony Meola, projections by Elaine J. McCarthy, wig and hair design by Tom Watson, music supervision and arrangements by Stephen Oremus, orchestrations by William David Brohn, dance arrangements by James Lynn Abbott, musical staging by Wayne Cilento and musical supervision-direction by Gareth Valentine.

Based on Gregory Maguire's novel, which turned every Oz myth inside out, Wicked explores the early life of the witches of Oz: Glinda and Elphaba. The two main characters meet at Shiz, a school where both hope to take up sorcery. Glinda is madly popular and Elphaba is, well, green. By a misunderstanding, they wind up roommates and, after an initial period of mutual loathing, begin to learn something about each other. Their life paths continue to intersect through a shared love, entry into the Emerald City and interaction with the Wizard himself. Eventually, their choices and convictions take them on widely different paths. For more on Wicked, which is booking until June 30, call (0)870 594 9494.