Percival Stainer Deslandes was born in Islington, London, England in late 1874 (his birth was registered in the last quarter of that year). He was baptised in All Saints Church, Battle Bridge, Islington on 31 January 1875 and he was the son of Theodore Philip Deslandes (1844-1924), a draper, and Clara Chamberlain (1843-1925). Both his parents were Channel Islanders, his father hailing from St Helier, Jersey and his mother from Guernsey, and they were married in London in 1871. He had one known sibling, Ada Matilda (b. 1872).

Percival, known as Percy, first appears on the 1881 census when he, his mother and sister were living at 6 Trinity Road, Weymouth, Dorset. His father, now a commercial traveller, was absent. They have shifted to number 4 Trinity Road, Weymouth by the time of the 1891 census and his father is again absent.

On June 1897 he was listed (in UK Railway Records) as a 3rd Steward aboard the vessel Victoria.

In 1901 he was working as a 2nd steward aboard the SS Roebuck moored at St Helier as listed in the Channel Islands census for that year.

Percival was married in Southampton in late-1910 to Elizabeth Myra Jones (b. 8 April 1879 in Southampton) but they would have no children. They appear together on the 1911 census living at 405 Portswood Road, Southampton and Percy was described as a steamship steward.

When he signed-on to the Titanic, on 4 April 1912, Percy gave his address as 405 Portswood Road (Southampton). His last ship had been the St Louis. He gave his age was 30 (he was 37).  As a first class saloon steward he received monthly wages of £3 15s.

Deslandes died in the sinking. His body was later recovered by the Mackay-Bennett (#212) and he was buried at Fairview Lawn Cemetery, Halifax, Nova Scotia on 6 May 1912.

His estate, worth £185, 3s, 8d was left to his widow Elizabeth. Elizabeth Deslandes never remarried and remained in Southampton where she died in 1961.

Hard on the heels of Percy's death came the death of his sister Ada on 29 June 1912. His parents continued to live in Weymouth, Dorset and died there in the 1920s.