She began her career with the George Mitchell Singers and made her first radio broadcast as a child in "Round the Horne".
Round-robin tournament | Lena Horne | Marilyn Horne | Round Rock, Texas | Sheila Horne | round-robin tournament | Round Here | Long Way Round | Round Table | Round shot | Shot Heard 'Round the World (baseball) | Series A round | Ring Round the Moon | Two-round system | Shot Heard 'Round the World | Round Top, Texas | Round the Twist | Round Table (Camelot) | Round Rock | Little Round Top | John Horne Tooke | Uruguay Round | Tom Horne | Round Rock Express | Pendleton Round-Up | Mathew Horne | Kenneth Horne | Donald Horne | Carina Round | A Voyage Round My Father |
Mortimer later wrote series for radio such as Men from the Ministry and Round the Horne, before writing many TV situation comedies including Foreign Affairs, Man About the House, Never the Twain, Robin's Nest and George and Mildred, often working in partnership with Brian Cooke.