Luca Giordano, 'The Martyrdom of Saint Januarius', about 1690

This painting was made as a preliminary study for the altarpiece of a chapel dedicated to Saint Januarius in S. Spirito dei Napoletani in Rome. This was the church where resident and visiting Neapolitans worshipped, and Saint Januarius would have had special significance for them. He became Bishop of Benevento near Naples at the age of only 20, but was martyred along with some of his followers in AD 305, during the persecution of Christians by the Roman Emperor Diocletian.

Saint Januarius was adopted as the patron saint of Naples – the city’s cathedral was dedicated to him, and his head and body were buried in the crypt. Now known by his Italian name, Gennaro, he is still famous today because of a supposed miracle that happens three times a year, when an ampoule containing his solidified blood liquefies. Thousands of people celebrate the event in a special cathedral service each time it happens.

Giordano has presented us with the moment immediately before the saint’s decapitation. The brightly lit Januarius kneels on a high rock at the very centre of the painting, which forms a sort of natural sacrificial altar. At its base are the bodies – including a bloody severed head – of those who have gone before him. The saint’s arms are open in supplication while, behind him, the executioner is already drawing his sword ready to strike the blow. In the distance, a gesturing figure in a turban urges the executioner on. Januarius’ death is anticipated by an angel, who has just arrived at speed and holds a pose which directly echoes that of the saint. In the angel’s left hand is a palm leaf – the emblem of martyrdom.

The structure of the composition reflects the imminent trajectory of the executioner’s sword. A strong diagonal sweeps down from the heads of the executioner and saint, following the slope down to the other victims’ bodies. It is echoed by both a rift in the rock and the line of onlookers filling the foreground, whose contrasting emotional states are reflected in their body language. The lounging guards look up expectantly, but the two women – and the child beside them – signal their distress and turn towards each other in anxiety.

Giordano was famous for his ability to work quickly and this painting, which is only a sketch, is testament to his skill in creating an accurate impression with remarkable economy. The angel’s right wing is suggested with barely a dozen decisive brushstrokes, while the volume and movement of his robes is evoked with a flurry of deft white highlights. But there are touches of great precision too – in the foreshortening of the little boy’s limbs, hand and foot in the right foreground, for example, and in the highlights which capture the glints of light on the soldiers’ helmets.