Douglas was an animal, sporting and genre painter, and follower of Landseer. He intended to train as a solicitor, but following an accident, turned to painting. His first picture was accepted at the Royal Scottish Academy at the age of 17. In the early years of his career he painted pictures for Sir Charles Tennant and had an early success with his paintings of Jersey cattle, one of which: Prize Jerseys, showed three famous animals from the herd of Lord Blyth. He was subsequently elected an Honorary Life member of the English Jersey Cattle Society. He painted horses, including two Derby winners, sheep, cattle and dogs. In later years he concentrated on scenes of Highland cattle and Shetland ponies in the snow. On his marriage he bought the Old Manor House, Lawnbrook, Shere, Surrey, moving in 1892 to Findon, Sussex, for his health. His wife published Art and Animals (privately printed), a copy of which was accepted by Queen Victoria.

Foaled in 1893, by St Simon out of Perdita, Persimmon was the full brother to Diamond Jubilee, another of the Prince of Wales's successful racehorses. 1896 was a triumphant year for Persimmon as he won the Derby, St. Leger and Jockey Club Stakes at Newmarket. He died of a fractured pelvis in 1908, aged fifteen.

Persimmon appears against a minimal background that suggests, rather than asserts, a stable interior: the dark blue horse blanket on the floor bears the feather insignia of his owner, the Prince of Wales. The stark composition and matter-of-fact presentation of the animal is reminiscent of the horse paintings of the previous century, notably the work of George Stubbs (1724-1806), though the treatment of the animal has a smooth, graphic quality that looks forward to the commercial art of the next century.

The painting was received at Marlborough House in July 1897; Dighton Probyn wrote to Sir James Blyth on 20 July thanking him the 'excellent likeness of the gallant horse'. However, later he wrote commenting that the Prince of Wales was delighted with the painting, but found the depiction of the straw to be the weak point, asking whether the painting should be returned to the artist to improve the straw. Douglas confirmed later that he only saw Persimmon in the sunshine once, at the Eclipse Stakes meeting in the paddock at Sandown, and only had a week to complete the painting.

Queen Victoria purchased an oil painting by Douglas from Henry Graves & Co, to be presented to the Prince of Wales on his birthday on 9 November, 1873. This was almost certainly 'The First of September', two spaniels chasing a partridge; a larger version of which was exhibited at the Royal Academy in 1871 (102). The painting was recorded at Marlborough House in 1877 and in Buckingham Palace in 1911.