Aged 16 Kelly appeared at the Prince's Theatre on Shaftesbury Avenue in the pantomime Cinderella opposite Derek Roy as Buttons and Christine Norden as Prince Charming. She next appeared as Irene Collins in the play Cosh Boy (April 1951) at the Embassy Theatre in Swiss Cottage in London,Cosh Boy by Bruce Walker, Cadbury Research Library, University of Birmingham playing the same role when the play was renamed Master Crook when it transferred to the Comedy Theatre in December 1951. Moiya Kelly (now Mrs John Bewsher) With Her Cat Sooty. Last Night She Made West End Stage Debut In Master Crook, Shutterstock websiteJ. P. Wearing. Master Crook, The London Stage 1950-1959: A Calendar of Productions, Performers, and Personnel, Rowman & Littlefield (2014), p. 138 Google Books Kelly was disappointed not to be offered the role of Irene Collins in the film Cosh Boy (1953), with the part going to Joan Collins.
