Anita Dobson is joining the cast of Wicked as part of the musical's 10th anniversary celebrations at Apollo Victoria Theatre.
The former EastEnders actress, 67, will play Madame Morrible, headmistress of Shiz University, from September until January 2017.
Celebrated Wicked alumnae Rachel Tucker, who returns from playing Elphaba on Broadway, and Suzie Mathers, who joins as Glinda from the Australian production, are also part of the special cast.
Northern Irish actress Rachel, who played Elphaba on the London stage from 2010-2012, is the longest running actress in the role in the West End show's history with over 900 performances to her name.
Based on the best-selling novel by Gregory Maguire, Wicked tells the story of the unlikely friendship formed between two witches as they study sorcery at Shiz and how they fulfil their destinies as Glinda The Good and the Wicked Witch of the West in the land of Oz.
Wicked celebrates 10 celebrates on the London stage on September 27, making it the eighth longest-running show in the West End and gaining two Olivier Audience Awards and nine What's On Stage trophies among the accolades during its run.
In the rest of the cast, Oliver Savile continues as love-interest Fiyero and Mark Curry as The Wizard. Original cast member Martin Ball returns to play Doctor Dillamond and Katie Rowley Jones plays Nessarose, while Idriss Kargbo joins to play Boq.
The 10th anniversary cast will lead the show from September 5, although Anita and Rachel will only appear until January 28, 2017.
Tickets for the 10th birthday performance will go on public sale on May 27 at 12.00pm at www.WickedTheMusical.co.uk/Wicked10.