 His father had a distinguished career in the British Army including appointments as director of artillery at the War Office (1930 to 1934) and in India (1934 to 1938).Hezlet joined the Royal Navy in January 1928, aged 13.He attended the Royal Naval College, Dartmouth and the Royal Naval College, Greenwich, and went to sea in 1932, serving as a midshipman on the battleships HMS "Royal Oak" (September 1931 – January 1934) and HMS "Resolution" (March – July 1934).