Der eingebildete Kranke
Kaiser was interned during the early days of the war, but was eventually released, changing his name in honour of his new home, Sydney. He became musical director for the Colgate-Palmolive radio unit, and was involved in theatre, running Sydney's Theatre for Children (1944–45) and co-founding the Mercury Theatre with Peter Finch. He produced the famous production of Molière's "The Imaginary Invalid" that was seen by Laurence Olivier and Vivien Leigh which led to them inviting Peter Finch to England.