The 39-year-old had no hesitation crossing the English Channel with the troops when war was declared, though he might have been justified remaining in London. He had two young children and his skill and reputation as an eye specialist was growing. At the outbreak of war, McNab was clinical assistant in the ophthalmic department of Charing Cross Hospital, and in practice in Harley Street.
Among his patients was Foreign Secretary Sir Edward Grey, whose address to the House of Commons on August 3, 1914, inspired Britain's Parliament to commit to the conflict in Europe. The day after his speech, Grey looked out from his desk and saw a man lighting gas lamps in St James's Park below. "The lamps are going out all over Europe," Grey said to his companion. "We shall not see them lit again in our lifetime."
McNab's Scottish parents were Southland farmers. His father Alexander was a prominent southern politician, while his older brother Robert served in William Massey's wartime National Ministry as Minister of Justice. Angus went to Southland Boys High, before enrolling at Otago University and completing two degrees. In 1896, McNab left his family for Scotland and medical studies at Edinburgh.
McNab also threw himself into sport. He was elected athletics club president and was a forward in the rugby team.
At the outbreak of the Boer War, he volunteered his services before returning to Edinburgh as a house surgeon at the Royal Infirmary's eye department.
He completed further studies in Germany at historic Freiburg University, where he learned to speak the national language and became an accomplished French and German scholar.
After August 1914, McNab went to war with London Scottish. One of his early acts was to train 100 men from the regiment as stretcher-bearers. He dealt with casualties from the battlefronts at Marne and Oise. McNab's special skill, according to his colleague Sir Frederick Milner, was detecting gangrenous wounds.
The action which claimed McNab's life took place when his regiment stormed the village of Messines.
A despatch rider stated the doctor was bayoneted as he bent down to help two wounded men. One account stated it was a bright, moonlit night, and the unarmed McNab had a Red Cross on his arm and was wearing a blue tunic.
His Scottish mates called it a "foul deed" and went after the Germans, giving orders that no prisoners should be taken.
New Zealand doctor Arthur Martin described McNab's killing in a letter to his brother Elias.
McNab, Martin wrote, an old university friend, was stabbed in five places.
"He is now dead poor fellow."
Royal Army Medical Corps records give the date of his death as November 1, 1914. The New Zealander is commemorated on the Menin Gate Memorial in Belgium.
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