Mendl was born in Kensington, the son of
Jewish Czech-born grain importer and shipowner Ferdinand and Jeanette Rachel Mendl. He was educated at
Harrow School and
University College, Oxford, graduating with second-class honours in Jurisprudence, and was called to the bar at the
Inner Temple. Mendl was a grain importer, like his father, and served as president of the
London Corn Trade Association from 1909 to 1912 and again from 1915 to 1919, and on the Royal Commission on Wheat Supplies until 1920. From 1915 to 1918, he was also a member of the War Office Advisory Committee on Army Contracts. He was appointed Vice President of the
World Services Group in 1938. == Political career ==