[1] Born in Sydney in 1894[2] He wrote over thirty screenplays in the United States and Britain, often collaborating with the director Carol Reed.
"[6] A 1931 profile said he was educated at the University of London and had directed a Malayan picture called Black Sands "which created a lot of excitement in Europe".
He also sold a story he wrote about the Sino-Japanese war called Shanghai Interlude which was going to be made by director John Ford and star Lew Ayres.
Wellesley wrote a series of films for Associated Talking Pictures, the forerunner of Ealing Studios: Love, Life and Laughter (1934) with Gracie Fields and Java Head (1934) with Anna May Wong directed by Thorold Dickinson; the latter had Carol Reed as assistant director.
He was loaned out to work on the script for Death Drives Through (1935), independently done at Ealing, then helped write a comedy, No Limit (1935) for a new star, George Formby.
[22] It was bought by 20th Century Fox who turned it into Night Train to Munich (1940), directed by Reed and written by Frank Launder and Sidney Gilliat.
Wellesley turned director with The Silver Fleet (1942), a film whose storyline was based on a suggestion of President Roosevelt.
He wrote and directed it in tandem with Vernon Sewell, replacing Clive Brook, and the film was produced by Powell and Pressburger.
[29] He wrote episodes of Douglas Fairbanks Presents as well as the features The Green Scarf (1954) and The March Hare (1956) Most of his later work was for TV: The Gay Cavalier, White Hunter, The Young Jacobites, International Detective, Sir Francis Drake and Beware of the Dog.
He still wrote features such as The Malpas Mystery (1960), Passport to China (1961) (for Hammer), Dead Man's Evidence (1962), and Doomsday at Eleven (1962).