This article investigates replication in the studio of Velazquez in Seville, focused on a little known version from the FitzHerbert Collection, Derbyshire, of the celebrated portrait in the Prado of Sor Jéronima de la Fuente. Direct comparison with the full-length Prado portrait and with a third version from the Araoz Collection suggests that the FitzHerbert Collection picture is an autograph replica that was subsequently cut down. X-rays of all three pictures confirm the belief that they were all made using the same cartoon or drawing, virtually excluding the possibility that they could have been executed anywhere except in Velazquez's own studio. Pentimenti and a more exploratory technique confirm that the Prado picture is the original version. The FitzHerbert picture may precede the Araoz version: the luminous reserved area around the entire figure, the highlights around the edges of her wimple and habit, especially her right sleeve, are as lively and vibrant as the equivalent passages in the Prado picture, suggesting it is closer in technique to the latter than to the more thinly painted Araoz picture.