Captain Brooke was born in Caxton, Cambridgeshire, on 31 March 1863. He was educated at Epsom College before studying medicine at the London Hospital. After a break in his studies, he qualified as a doctor in November 1894. On 16 October 1885, he married Constance Blanche Moore. The couple had seven children, Cecil, Olive, Nora, Margaret, Sylvia, Dorothy and Lancelot. Their son Second Lieutenant Cecil Rupert Brooke was killed on 24 April 1917 whilst serving with 8th Battalion The Gordon Highlanders and is commemorated on the Arras Memorial.

Cpt Brooke was Commissioned into the Royal Army Medical Corps on 10 July 1915 and initially took charge of wards at Sidmouth Barracks. He went on to serve onboard HMS Britannic, the sister ship of the Titanic, which had been requisitioned as a hospital ship after the outbreak of the First World War. The ship was ultimately sunk after hitting a German mine on 21 November 1916 in the Aegean Sea. Captain Brooke went on to serve at Thornhill Camp near Winchester and at a convalescent hospital in France before becoming the Medical Officer of 1st Battalion The Wiltshire Regiment.

The War Diaries of 1st Battalion The Wiltshire Regiment show that at 21:15 hours on 26 May 1918, they took up positions in front of Guyencourt. At 01:00 hours on 27 May, the first day of the Third Battle of the Aisne, the enemy began a heavy gas bombardment, which lasted until 05:00 hours. At that point they began to attack the forward battalion line held by 8th Division.

At 07:00 hours 1st Battalion The Wiltshire Regiment were ordered to move forward to cover the retirement of frontline troops, before at 10:15 hours, moving forward again to hold the line in front of Bouffignereux. The enemy constantly shelled the Battalion HQ and gun fire swept across the roads and tracks leading to it. The Regimental Aid Post, from which Captain Brooke would have operated, was located in a small quarry close to the Battalion HQ.

At 17:40 hours the enemy attacked again, and 1st Battalion The Wiltshire Regiment were forced to retreat. They split into small parties as they retired and fought small rear-guard actions. Captain Brooke was killed, age 55, during the fighting that day.

The grave of Capt Brooke was found after a researcher submitted evidence suggesting that his grave could be identified. Further research conducted by the National Army Museum and the MOD’s Joint Casualty and Compassionate Centre (JCCC) confirmed their findings. Cpt Brooke's final resting place was rededicated in September 2023 and is now marked with a CWGC headstone in perpetuity.