He was born Marcel Hyacinthe le Bozec in Paris, France.
Varnel started his working life on the Paris stage, soon becoming a director of musical comedies.
In 1925, he moved to New York City, working as director in several Broadway operettas, musicals and dramas for the Shubert family.
Among the performers he worked with were Will Hay, The Crazy Gang, Arthur Askey and George Formby.
He died on 13 July 1947 in a car crash near Rake, West Sussex.