Ernest Rousseau was Professor of Physics who later became the Rector of Brussels University. Ensor was introduced to him by Rousseau’s brother-in-law Théo Hannon. The Rousseaus lived at 20, rue Vautier, Brussels, where they entertained literary and artistic friends including Félicien Rops and Eugène Demolder. Ensor became a close friend of the family and a room was always kept for him in the house for his frequent visits to Brussels (see also lots 20, 21, 23, 26 & 27). This fine portrait pays tribute to Rousseau, who - following the death of Frédéric-James Ensor in 1887 – became something of a substitute father for the artist.