Arnold had a successful public service career during the First
World War as British Civil Commissioner in Baghdad and as the
colonial administrator of Mesopotamia.
In 1933 he was elected as the Member of Parliament for Hitchin
in Herefordshire. Upon the outbreak of the Second World War, he
joined the RAF and served as an air gunner. On 31 May 1940 he
became the third serving MP to die during the conflict when his
Wellington Bomber crashed during the Battle of France.
He is buried in Eringhem Churchyard, France.