Todd spends a few of his childhood years in India, where his father, an officer in the British Army, serves as a physician. Later his family moves to Devon and he attends Shrewsbury School. Upon leaving school, he trains for a potential military career at Royal Military Academy Sandhurst before beginning his acting training at the Italia Conti Academy of Theatre Arts in London. This change in career leads to estrangement from his mother. When he learns at age 19 that she has committed suicide, he does not grieve long for her, he admits in later life.
Todd first appears professionally as an actor at the Regent’s Park Open Air Theatre in 1936 in a production of Twelfth Night. He plays in regional theatres and then co-founds the Dundee Repertory Theatre in Scotland in 1939. He also appears as an extra in British films like Good Morning, Boys (1937), A Yank at Oxford (1938) and Old Bones of the River (1939).
At the beginning of World War II, Todd enlists in the British Army, receiving a commission in 1941. On June 6, 1944, as a captain, he participates in Operation Tonga during the Normandy landings. He is among the first British officers to land in Normandy as part of Operation Overlord.
After the war, Todd is unsure what direction to take in his career. His former agent, Robert Lennard, has become a casting agent for Associated British Picture Corporation and advises him to try out for the Dundee Repertory Company. He does so, performing in plays such as Claudia, where he appears with Claudia Grant-Bogle. Lennard arranges for a screen test and Associated British offers him a long-term contract in 1948. He is cast in the lead in For Them That Trespass (1949), directed by Alberto Cavalcanti. The film is a minor hit and his career is launched.
Having portrayed the role of Yank in the Dundee Repertory stage version of John Patrick‘s play The Hasty Heart, Todd is subsequently chosen to appear in the 1948 London stage version of the play, this time in the leading role of Cpl. Lachlan McLachlan. This leads to his being cast in that role in the Warner Bros. film adaptation of the play, which is filmed in the United Kingdom, alongside Ronald Reagan and Patricia Neal. He is nominated for the Academy Award for Best Actor for the role in 1949.
Todd is now in much demand. He appears in the thriller The Interrupted Journey (1949), Alfred Hitchcock‘s Stage Fright (1950), opposite Marlene Dietrich and Jane Wyman, Portrait of Clare (1950), Flesh and Blood (1951), The Story of Robin Hood and His Merrie Men (1952), 24 Hours of a Woman’s Life (1952), with Merle Oberon, Venetian Bird (1952), The Sword and the Rose (1953) and Rob Roy, the Highland Rogue (1953). In 1953, he appears in a BBC Television adaptation of the novel Wuthering Heights.
Todd’s career receives a boost when 20th Century Fox signs him to a non-exclusive contract. He appears the film version of Catherine Marshall‘s best selling biography, A Man Called Peter (1955), which is a popular success. Other films in which he appears include The Dam Busters (1955), The Virgin Queen (1955), Marie Antoinette Queen of France (1956), D-Day the Sixth of June (1956), Yangtse Incident: The Story of H.M.S. Amethyst (1957), Saint Joan (1957), Chase a Crooked Shadow (1958), Intent to Kill (1958), Danger Within (1958), Never Let Go (1960) and The Long and the Short and the Tall (1961).
Todd’s career in films rapidly declines in the 1960s as the counter-culture movement in the Arts becomes fashionable in England, with social-realist dramas commercially replacing the more middle-class orientated dramatic productions that Todd’s performance character-type had previously excelled in.
In retirement, Todd lives in the village of Little Ponton and later in Little Humby, eight miles from Grantham, Lincolnshire. Suffering from cancer, he dies at his home on December 3, 2009. He is buried between his two sons, Seamus and Peter, at St. Guthlac’s Church in Little Ponton, Lincolnshire, England.