Alfred de Bathe Brandon was born on 21 July 1883 in Wellington, New Zealand, the son of Alfred de Bathe Brandon, a solicitor, and his wife, Louisa Kebbell. His father was mayor of Wellington from 1893 to 1894 and his grandfather, also named Alfred de Bathe Brandon, was an early Wellington settler, crown prosecutor and MLC. He was educated at Wellington College (1894–1901) and Canterbury College; then he went to England where he studied law at Trinity College, Cambridge. After being called to the Bar at London's Middle Temple in 1906, he returned to Wellington to join his father's legal firm of Brandon, Hislop and Johnston.
Brandon developed an interest in flying and, following the outbreak of war with Germany in 1914, returned to England. He learned to fly at the Hall Flying School at Hendon at his own expense, and on 17 October 1915, after seven weeks' instruction, he qualified as a pilot. In December 1915 he joined the Royal Flying Corps and in January 1916 was commissioned as a second lieutenant.
In recognition of his courageous attacks on Zeppelins during their raids on eastern England in 1916, Alfred de Bathe Brandon was awarded the Military Cross and then appointed a DSO; he was also mentioned in dispatches. He became an overnight celebrity when he was credited with the destruction of the first Zeppelin brought down over England. However, investigations soon concluded that anti-aircraft fire had inflicted the crucial damage that caused Zeppelin L-15 to crash in the sea some miles off the Thames Estuary. But Brandon's assault on L-15, at 9,000 feet while being subjected to enemy machine-gun fire, and his subsequent attack on Zeppelin L-33 on the night of 23 September, helping to bring the airship down in a field, were brave and daring acts which were recognised by the British government. Brandon flew a BE2c single-engined biplane in these engagements. Regular promotions followed and he was commissioned as a major in January 1918. When the Royal Flying Corps and the Royal Naval Air Service were amalgamated on 1 April 1918 to become the Royal Air Force, he held this rank in the new service.
In May 1919 Brandon returned to New Zealand a war hero. Although he never flew again he did make a further contribution to military aviation. On his departure from Britain he was assigned to assist Colonel A. V. Bettington, a senior RAF officer, who was to advise the New Zealand government on the requirements for the country's air defences. After thoroughly appraising existing and potential airfields, Brandon prepared that section of Bettington's report dealing with landing grounds. The task took him six months and afterwards he returned to law.
Alfred de Bathe Brandon married Ada Mabel Perry at the Cathedral Church of St Paul, Wellington, on 2 January 1942; he was 58, she 38. They had one child, Peter de Bathe Brandon. After retiring in the 1950s Brandon continued to pursue his leisure interests of horse-racing, golf and fishing. However, the death of his son in a road accident in October 1969 left him grieving. He died in Upper Hutt on 19 June 1974, survived by his wife.