Prince Baltasar Carlos (1629–1646) was the son of Philip IV of Spain by his first Queen Isabel de Bourbon. He was idolized by his parents but died of fever at the age of fifteen in 1646. Here he is shown aged about three years old. Despite the demands of etiquette, the formality of pose and the stiffness of dress, the picture demonstrates Velázquez’s consummate ability to evoke the spirit of childhood. Although he paid a ‘prodigious price’ for the picture (1,600 guineas), the 4th Marquess of Hertford seemed well pleased with his purchase when he saw it in 1855, writing to his agent Samuel Mawson that ‘the Velázquez is beautiful’.