In 1918 Donald de Carle was elected a fellow of the British Horological Institute and in the same year joined The Goldsmiths and Silversmiths Company, 221 Regent Street, London, which amalgamated with Garrards & Co in 1952. He remained in full time employment working five and a half days a week with the latter company, which was eventually owned by the entrepreneur Sir Charles Clore, until his retirement at the age of 75 in 1968.
The Goldsmiths and Silversmiths Company first appointed him to work in the workshop of the Watch and Clock Department. He then became Workshop Manager eventually becoming Manager of the whole department which included sales and buying. When Clore took over Garrards in 1957 he was also appointed watch and clock buyer for Mappin and Webb, a Clore company.