The sketch was made for one of Whistler’s most valuable patrons, the banker William Alexander, who was buying his work when many thought his art was recklessly modern. He had bought the first of the artist’s famous Nocturnes. A later one would lead to a famous libel action when Whistler sued the critic John Ruskin for describing it as “flinging a pot of paint in the public’s face”, and was almost bankrupted when he won but was awarded a farthing damages.

Alexander also bought Arrangement in Grey and Black No 1, better known as Whistler’s Mother. The artist then offered to paint the banker’s eight-year-old daughter, and gave him the pastel sketch – his first ideas for the portrait. He was already working on a portrait of her older sister May, but promised that Cicely would get his full attention.

Whistler said: “I should work at the present moment with more freshness at this very fair arrangement I propose to myself than any other.” The final portrait became one of his most admired works, now in the Tate collection: Harmony in Grey and Green – Miss Cicely Alexander.