A ‘symphony of hands’ is how the curator Francesca Whitlum-Cooper describes the Martyrdom of St Ursula, the final painting attributed to the great Renaissance master Caravaggio and now the focus of the National Gallery’s new single-room exhibition, The Last Caravaggio. If symphony is a fitting term – hands are certainly prominent, and drive the intense narrative – then the painting is Bruckneresque in its brooding, unflinching majesty, the very definition of chiaroscuro, and a long way from the classical, springy, airy melodies of a Haydn or Mozart – or a comparable work by contemporaries such as Caracci or Carpaccio, who dealt with the same subject on vast, crowded, canvases, emphasising beauty and colour rather than distress in the shadows.

The work’s tenebrous marvels are revealed alongside the National Gallery’s only Caravaggio currently on display, Salome Receives the Head of John the Baptist – painted the previous year, in similar, unflinching style – in the appropriately sepulchral Room 46. Within 10 weeks of the creation of his final masterpiece, Caravaggio, as we now know Michelangelo Merisi, a stonemason’s son from Lombardy, was dead, a little shy of his 40^th birthday. Did a facial wound – he was slashed grotesquely outside a tavern by avengers – become infected, or was he the victim of the malaria rife in the mezzogiorno? We may never know, despite his pathetic, lonely, pauper’s death in Porto Ercole being a matter of historical record.

The subject of Caravaggio’s last painting is derived from The Golden Legend, a biography of 150 or so saints compiled by Jacobus de Varaigne in the middle of the 13^th century. St Ursula was a British or Breton princess, who was returning from a pilgrimage to Rome, when, in Cologne, she and her virginal followers – the numbers are disputed; some claim 11,000 – were captured by the king of the Huns, who, entranced by her beauty, asked for her hand in marriage. She refused, a testament to her Christian faith, and the king ‘shot at her an arrow, and pierced her through the body and so accomplished her martyrdom’.

The Martyrdom of St Ursula also stands as the last self-portrait of the artist; the crop-haired figure behind the martyr, of grim, deathly pallor who looks into the void – though his facial disfigurement is hidden. And then there’s the hands. A soldier’s hand supports Ursula in anticipation of her crumpling. The archer, who has fired the arrow into her chest, looks at her with a mixture of pity and despair, his hands still quivering from his action, the bow still vibrating. The hand of another, at the centre of the work, newly apparent following a recent restoration, attempts an intervention, but too late. Ursula herself, cups her breasts to focus on the mortal wound, a moment of grace in the face of death.

Part of Caravaggio’s appeal to the modern mind is that he is perceived as a rebel (‘whaddya got?’). Aesthetically, certainly, in his cold-eyed realism, of dirty fingernails and low-life models. In his personal conduct, perhaps ‘thug’ might be a better description than rebel, as it often is when stripped of romance. He seems to have had an uncontrollably violent temper, which culminated in him killing a man, Ranuccio Tomassoni, on a tennis court in Rome in 1606. With a bando capitale on his head – meaning he was fair game for any citizen of the Papal States – Caravaggio headed to Naples: seething, vast, chaotic. His next destination was its opposite: orderly Malta, where he was successful in joining the Knights of St John. Inevitably, his temper got the better of him, and he ended up in a Maltese dungeon, from which he escaped in cinematic style. Next stop, Sicily, where he painted arguably his greatest work – Burial of St Lucy – for the church of Santa Lucia al Sepolcro in Syracuse’s Manhattan-like island, Ortygia. Whatever the state of his personal life, he never lost his muse, and it culminated in the two paintings now on display, which are unmissable.

The story of The Martrydom is almost as remarkable as the artist who painted it. Until recently it was thought to be the work of either Bartolomeo Manfredi (1582-1622), a Roman contemporary of Caravaggio, or the Calabrian artist Mattia Preti (1613-99), heavily influenced by him. The art historian Mina Gregori had suggested in the mid 1970s that it might be by Caravaggio, but proof was elusive until the discovery in 1980 by the scholar Vincenzo Pacelli of a letter in Naples’ Stato Archivo dated 11 May 1610.

It was in the hand of Lanfranco Massa, a factotum based in Naples who acted on behalf of the Genoese nobleman Marcantonio Doria. It spoke of a painting that Doria had commissioned from the man then considered to be Naples’ greatest artist: Caravaggio. Though the result was ecstatically and universally praised, Massa’s handling of the new painting left something to be desired:

‘I had intended to send you the picture of Saint Ursula this week, but to make sure of sending it perfectly dry I put it out yesterday in the sun, which, rather than drying out the varnish, made it soften, since Caravaggio applied it quite thickly; I will go round to said Caravaggio’s again to get his opinion on what to do so I can be sure of not ruining it; Signor Damiano has seen it, and was amazed, like everyone else who has seen it.’

The attribution was further enhanced when two inscriptions were revealed on the back of the original canvas. One of the artists, D. Michel Angelo da / Caravagio; the other of the patron, ‘M. A. D.’. A lost Caravaggio became the last Caravaggio.

Normally, The Martyrdom of St Ursula is displayed in the Gallerie d’Italia on Naples Via Toledo, at the bustling heart of the most pulsating city in Europe – where Caravaggio trod – restored by its owners, Banca Intesa Sanpaolo. Every lover of art is in their debt, and London’s National Gallery has created a fitting, temporary space for this valedictory masterpiece.

The Last Caravaggio runs until 21 July at the National Gallery in London. Admission is free.