In addition, Sam Kelly will return to the role of the Wizard that he previously played in the show in 2009-10.
They join Katie Rowley Jones and Sam Lupton, who will continue in their current starring roles as Nessarose and Boq, respectively. Emma Hatton will be standby for the role of Elphaba, and current ensemble cast member Sophie Linder-Lee will become standby for the role of Glinda.
Louise Dearman (Elphaba), Gina Beck (Glinda), Ben Freeman (Fiyero), Harriet Thorpe (Madame Morrible), Keith Bartlett (The Wizard), Christopher Howell (Doctor Dillamond), Hayley Gallivan (standby Elphaba) and Lucy van Gasse (standby Glinda) will all play their final performances Nov. 16.
Stevenson was last seen in the West End as Sybil Evers in Chariots of Fire at the Gielgud Theatre. Other West End appearances include Gone with the Wind at the New London and Mary Poppins (Prince Edward), and elsewhere Aspects of Love (Menier Chocolate Factory).
Kelvin has played a long run as Matron "Mama" Morton in Chicago in the West End at both the Adelphi and Cambridge Theatres. Other West End musical credits include Golde in Fiddler on the Roof (Savoy), Widow Corney in Oliver! (London Palladium) and Madame Thenardier in Les Miserables (Palace Theatre).
Clarkson created the role of Harry Bright in the original London production of Mamma Mia! at the Prince Edward Theatre. He previously won an Olivier Award as Best Actor in a Musical for his performance in the West End premiere of Howard Goodall and Melvyn Bragg's The Hired Man.
Kelly has appeared in many long-running television series including "Porridge," "'Allo, 'Allo," "Now and Then," "Haggard," "On The Up," "Holding On" and "Barbara" with Gwen Taylor. More recent appearances include "The Charles Dickens Show," "Outnumbered," "My Family," "Magic Grandad" and the film "Nanny McPhee and the Big Bang." He has worked frequently with the director Mike Leigh, appearing in the films "Grown-Ups," "Topsy-Turvy," "All or Nothing" and "A Running Jump" and on stage at the National Theatre in Leigh's Grief. Also at the National he appeared as Senex in A Funny Thing Happened On The Way To The Forum and was most recently seen in When We Are Married at the Garrick Theatre.
To book tickets, contact the box office on 0844 826 8000, or visit www.WickedTheMusical.co.uk for more details.