In the First World War he initially volunteered for the Royal Flying Corps, but transferred to the London Scottish Regiment. After being injured in the Battle of the Somme he was returned home to recuperate before transferring to Egypt. While in Egypt, on 1 May 1918, he volunteered to carry a message along the front line where he was hit several times by a sniper. For his continued attempts at climbing the slopes of a wadi whilst wounded and under sniper fire, he was awarded the Victoria Cross. After the war he returned to business work before moving to Southend. After serving in the Home Guard as a Major in the Second World War, he served on several local organisations and committees before dying in Leicestershire in 1961. His medal was donated to his regimental museum.
Cruickshank was born in Winnipeg in 1888, the first born of 5 children. His two brothers and two sisters were born in England. His youngest brother, John, died at the age of 10 in 1913, tripping as he alighted from a moving tram and fracturing his skull. He had been out shopping with a friend to buy a Scout's cape. His middle brother, Percy, also volunteered for the Army, and was killed while serving in the Royal Fusiliers on the Western Front in 1917, aged 19. He is buried in France.
Cruickshank moved to England at the age of 3; his father also called Robert originated from Aberdeen. His father had apparently been working with the Canadian Pacific Railway as an accountant. After the family arrived in England they initially lived in Islington according to the 1891 Census but by the 1901 Census had moved to Woodford. From 1903–1904 he was educated at Bancroft's School, Woodford, Essex. After leaving school, he worked as a travelling salesman, joining first Lipton, then the Lever Company. He was very interested in military matters and joined The City of London Yeomanry (Rough Riders), a volunteer unit 1908–1911.
At some stage his family moved to Harringay, North London, and he became involved in the Scouting movement shortly after it was established. He became an Assistant Scoutmaster. He was also involved in local politics and was noted as a good speaker. He supported Percy Alden MP in several election campaigns.
After war was declared, he initially volunteered for the Royal Flying Corps, but transferred to the London Scottish Regiment. After training he was initially posted to the 1st Battalion in France, where he was wounded at the Battle of the Somme in September 1916 at Leuze Wood.