In 1944, he was commissioned into the Royal Engineers Movement Control Section.
After the war he joined the diplomatic service and eventually served as a Trade Commissioner in Canada; Halifax, Nova Scotia; Winnipeg, Manitoba; and Kuala Lumpur, before becoming senior Trade Commissioner in Montreal, Quebec.
Cross went on to serve as Under-Secretary in various divisions of Britain's Department of Trade and Industry and Department of Energy.
In 1971, he was made a Companion of the Order of St Michael and St George (CMG).