Michelangelo's sculptural relief, the Taddei Tondo (c.1504–1505), is his only marble in Britain.
Named after the Florentine gentleman who acquired it directly from the artist, it is the greatest treasure of the Royal Academy's collection and was the centrepiece of a major redisplay when the Royal Academy celebrated its 250th anniversary in 2018.
For those in the know, the sculpture has been discreetly exhibited in the corridor of the Sackler Wing since the 1990s, in a specially designed niche behind bulletproof glass. It enjoyed an exceptional recent outing to London's National Gallery where, in the opening room of the 'Michelangelo & Sebastiano del Piombo' exhibition, it proved – for many – to be a revelation.
The tondo's importance lies not only in the fact that it is a significant work by this towering Renaissance genius, but it was also executed in the years between his famous colossal statue of David (1501–1504) and the Sistine Chapel Ceiling frescoes (1508–1512). It is also remarkable for its size – unusually large for a sculpted 'tondo' (a type of image named after its rotondo, round shape) – and for its innovative interpretation of the Madonna and Child theme, which packs a dramatic punch like no other.
‘Taddei Tondo’, The Virgin and Child with the Infant Saint John
(detail), c.1504–1505, marble relief by Michelangelo Buonarroti (1475–1564) 
But perhaps its most tantalising aspect is that it has been left in an 'unfinished' state, although one gets the sense that for Michelangelo – and for his adventurous buyer Taddeo Taddei – it was 'finished enough'. Michelangelo left a remarkable 26 out of some 43 of his marbles unfinished; in the tondo's case, progress was probably curtailed when he was summoned to Rome to work on Pope Julius II's tomb.
Thus each of the three figures exhibits a different state of 'completion', with the marks of the various chisels and hammer blows clearly visible. This gives us the vital sensation of almost looking over Michelangelo's shoulder as he carved, causing chips of marble to fly.
‘Taddei Tondo’, The Virgin and Child with the Infant Saint John
(detail), c.1504–1505, marble relief by Michelangelo Buonarroti (1475–1564) 
Like many other images in this fashionable devotional Florentine format, Michelangelo's tondo depicts the Virgin and Child and the infant Saint John in a landscape. The image is hewn from a great lump of Carrara marble, with the sparkling crystals animating the surface. The narrative, too, is unusually 'alive' for such a gentle theme.
The toddler Saint John – a shadowy, dynamic figure – holds out a fluttering bird, which startles the Christ Child as he rests on his mother's lap. Christ seems torn between his natural impulse to flinch and even run away (in fact, he almost propels himself out of the sculptural space) and being drawn irresistibly towards John's clumsy 'offering'.
‘Taddei Tondo’, The Virgin and Child with the Infant Saint John
(detail), c.1504–1505, marble relief by Michelangelo Buonarroti (1475–1564) 
The bird, variously identified as a dove or a goldfinch, is usually interpreted as a symbol of Christ's Passion or future sacrifice. The Virgin, a beautiful and remote figure, turbaned and veiled and in gentle profile, appears at that moment to foresee her child's momentous destiny, as it were, 'step by step'.
The figures are arrested, caught between past, present and future, and yet at the same time the boldness and virtuosity of Michelangelo's 'attack' makes the composition crackle with energy and possibility (visible in the flurry of chisel marks and his audacious working of the stone).
While the tondo hung in the Taddei residence, Taddeo's protégé – the precocious young Umbrian artist Raphael, who intermittently stayed there – eagerly made sketches of it, in the process transforming his provincial style.
‘Taddei Tondo’, The Virgin and Child with the Infant Saint John
(detail), c.1504–1505, marble relief by Michelangelo Buonarroti (1475–1564) 
After Taddeo's death, the tondo passed to his descendants, but the family's political and financial fortunes plummeted, with their palaces sold off. The tondo only publicly resurfaced in 1812, when it was bought by the French Neoclassical artist Jean-Baptiste Wicar, and again in 1822, when the elderly English connoisseur, collector and amateur landscape painter Sir George Beaumont acquired it from Wicar during his final continental tour (embarked on in the vain hope of educating his son).
Beaumont specified that his great tondo should be left to the Royal Academy, which acquired it in 1830, following his death in 1827. Beaumont's explicit intention was that every artist should have free access to it, so that progress in the arts could be promoted. The tondo is of course especially illuminating for artists, in that it lays bare Michelangelo's whole process from beginning to end.
Sketch of Michelangelo's Taddei Tondo
c.1823 (?)
David Wilkie 
The tondo was duly delivered to the Royal Academy in the summer of 1830 at the cost of a £1. The artist John Constable sketched it almost as soon as it arrived, describing it as 'one of the most beautiful works in existence'.
Sketch of Michelangelo's Taddei Tondo
1830
John Constable
For many, its mysterious play of light and shadow over the various surfaces makes it one of Michelangelo's most 'painterly' works – demonstrating not only his rivalry with his older contemporary Leonardo da Vinci but also the psychological intensity of Michelangelo's own response to the mother and child theme.
Alison Cole, author of Michelangelo: The Taddei Tondo, Royal Academy Publications, 2017
