He succeeded his brother Wilfred Stamp and father as Baron Stamp when they were killed during the war by German bombing. As they were killed together, English law has a legal fiction that in the event of the order of deaths being indeterminable, the elder is deemed to have died first. Legally therefore, Josiah is presumed to have died first and Wilfred momentarily inherited the peerage: and as a consequence the family had to pay death duty twice.