In 1911 he became the managing director of William Foster & Co. Ltd.
In May 1914 he is given a contract to work on a machine to combat the field works of barbed wire and trench warfare; this machine will be called the Tritton Trench Crosser and will be abandoned in June 1915.
In July 1915 he is awarded the contract to develop what will become the first British tank by the Landships Committee.
In 1916 he married Isobel Grahame Gillies.
In 1917 he was knighted for his work on the development of the tank.
On 6 October 1919 he is awarded 15,000 pounds for his work on the development of the tank, being official reconized as the co-creator, along with Walter Gordon Wilson, of the tank by the Royal Commission on Awards to Inventors.
In 1939 he becomes the chairman of William Foster & Co. Ltd.