Facts on Diego Polo have been emerging for the last thirty years. It is possible that he was from Burgos, the nephew of a painter of the same name who was resident in Madrid in 1607 and Alcalá in 1617, and who also appears to have been active at El Escorial. This may have led to training at the Court (he was assistant to Antonio Lanchares at the time of his death in 1630) and at the monastery of San Lorenzo, where he mostly studied Titian’s paintings.
This hitherto unknown picture clearly has all the characteristics that define the paintings attributed to him. This was mainly by Pérez Sánchez, based on the scarce information provided by Díaz del Valle and Palomino, the mention by Father Santos in his description of the Monastery school at El Escorial, the catalogue of the Infante Sebastián Gabriel’s collection and on some drawings.
The influence of Titian’s mature style, which was so determinant, is seen in the technique of a loose touch and separate brush strokes (the tree trunk, the lamb’s wool, the material and some anatomical profiles, as well as the warm colours with cold reflections – the carmines and whites of the symbolic martyr’s cloth), all contrasted with the dark greens of the landscape in the background. The composition resembles the St. Jerome in the Prado Museum, especially when one considers the positioning of the arms and the fact that the cheek is being supported by the hand. The straight line of the nose, the lengthening of the fingers (which are outlined without nuances), and the vulgarity of the boy, bordering on stupidity, are also significant factors. The branches and hanging leaves to the left are similar to those in other works by the painter.
Worthy of mention in terms of iconography are the lamb that is drinking water from the spring (which is repeated in a work from a private collection attributed to Cerezo), the complete inscription on the phylactery, and the background scene of Christ’s baptism, showing the dove in the sky.