Milles knew how to convey on paper and canvas a portrait similarity in early childhood and already then often painted portraits of his relatives and friends. Thus, the young artist tried to express gratitude to someone or his disposition to some person.
However, he seriously became interested in portrait painting only in the early 1870s. Among his customers were many famous people of the Victorian era: politicians, cultural figures, and even secular beauties, including Lady Campbell and Mrs. Perugini, the second daughter of Charles Dickens.
In the National Portrait Gallery in London, Milles can be found in portraits of two British prime ministers – William Gladstone, 1879 and Lord Salisbury, as well as portraits of actor Sir Henry Irving and composer Sir Arthur Sullivan.