Major Arthur Algernon Smith-Dorrien-Smith was born on 28 January 1876, in Oxfordshire, to Thomas Smith-Dorrien-Smith and Edith Anna Maria (née Tower). He married Eleanor Salvin Bowlby (died 13 April 1978), daughter of Edward Salvin Bowlby and Elizabeth Vans (née Agnew), on 11 May 1909 at Holy Trinity Church, Sloane Street, London.[3]
There were four sons and three daughters from this marriage:
Captain Algernon Robert Augustus Dorrien-Smith (5 May 1910 – 20 May 1940, buried in Lapugnoy Military Cemetery, Pas de Calais, France) married Rosemarie Helen Lucas-Tooth
On the death of his father in 1918, he succeeded as Lord Proprietor of the Isles of Scilly, a position he held until 1920 when the lease for the majority of the Isles of Scilly was handed back to the Duchy of Cornwall, Dorrien-Smith retaining control only over Tresco.
He continued the work of his father and developed Tresco Abbey Gardens making many trips to South Africa looking for suitable trees and plants. He went on the 1907 Sub-Antarctic Islands Scientific Expedition, which had as its primary object magnetic observation in the Auckland and Campbell Islands. Following the expedition he travelled widely in New Zealand, as well as making a shorter visit to Australia. In 1909 he again visited Australia, New Zealand and the Chatham Islands, and had a total collection of plants and seeds of about 2280 specimens. He was awarded the Victoria Medal of Honour by the Royal Horticultural Society in 1944.