He was born Horace Walter Gilbert-Williams on 6 April 1855 in the Kensington district of London, being the only child of the well-known Victorian landscape painter Arthur Gilbert and Gilbert's second wife Sarah Ann Godfrey.
He initially became a landscape painter, like his father, and his older step-sister Kate Gilbert, but ultimately he decided to pursue instead a career as a civil servant and university lecturer.
[1] He painted mainly landscapes of the Thames River and of the low hills near his home in Surrey, with many of his paintings showing water and/or meadows in the foreground, fronting dense thickets of dark green trees, against a backdrop of cloudy skies.
His use of dark greens contrast with the soft earth tones of stark mountain scapes that characterize much of the work of his father.
[2] He also painted several nice watercolors of his father's home at De Tillens in Limpsfield, Surrey.