Bronze bas-relief plaque in a carved wooden frame. The sitter, a balding bearded figure in a suit jacket, collar and tie, is shown head and upper torso, in left profile. In the top right corner is a heraldic crest of two raised arms gripping a horizontal staff, set above the Latin date 'MDCCCCIV' [1904]. The bronze is also signed in the lower right corner, on the figure's shoulder 'C. Fantachiotty fece Firenze', though the name of this Florentine sculptor (1844-1922) is usually recorded as 'Fantachiotti'.

Longstaff came from a wealthy colliery owning family, he was largely privately educated on the continent and later at the Royal College of Chemistry in London (then part of the Royal School of Mines). He subsequently had a successful 17-year business career in Hull, where he was one of the earliest to develop a successful profit-sharing scheme for his employees, but spent his last forty years in Wimbledon where he was a significant but unostentatious philanthropist, not least to the Red Cross during World War I. From the mid 1850s he was a notable traveller, especially in Canada, which he crossed five times. He became a Fellow of the Royal Geographical Society in 1870, serving for some years on its council, as well as belonging to the Meteorological and Zoological Societies, the Royal Institution and the Royal United Services Institution. He had a considerable interest in the Antarctic and he contributed £30,000 to Scott's 1901-04 British National Antarctic expedition in the 'Discovery'. From 1860 to 1880 he was in the Volunteer Division of the East Yorkshire Regiment, retiring as a lieutenant-colonel. All four of his sons were at some stage military or naval men, and his three daughters all married soldiers. His eldest son, Tom George Longstaff (1875-1964), was a mountaineer and explorer in the Himalyas and Tibet and the second son, Cedric, was a friend and supporter of Shackleton from 1900.

This relief portrait was presented to the Museum in 1979 by the sitter's grandson, C. C. Longstaff of Dunnington Manor, Bewholme, Yorkshire.