He remained in the occupation for six years before gaining a place at the Central School of Speech and Drama and training to become an actor.

It was a worldwide hit with runs on Broadway, Paris (with Gérard Depardieu), Madrid (with Concha Velasco), Berlin, Stockholm, Sydney, Rome (starring Domenico Modugno), Vienna, Prague and elsewhere.

His script for the 1970 film, which starred Peter Sellers and Goldie Hawn, won the Writers' Guild of Great Britain Award in 1970 for the Best British Comedy Screenplay.

Frisby's book, Outrageous Fortune (1998), is an autobiographical account addressed to his son, Dominic Frisby, about his fifteen years as a litigant-in-person in the High Court following his divorce in 1971 from the model Christine Doppelt and his custody claim involving their son, who is now an author and comedian.

He died in April 2020, aged 87,[4] from the side effects of treatment three years earlier for bladder cancer, which he did not have.