t’s not standard practice for curators to draw attention to a masterpiece they failed to borrow. But right in the middle of Tate Britain’s roaring whirlpool of a Turner exhibition is a reproduction of his 1840 painting Slave Ship (Slavers Throwing Overboard the Dead and Dying, Typhoon Coming On). Apparently, it has become too frail to make the transatlantic journey from Boston’s Museum of Fine Arts – another twist in the story of the most devastating work of art ever made about the British slave trade. So, instead of passing over its no-show, the exhibition demands you pause to mourn it – and what it depicts. This painting belongs at the heart of Turner’s Modern World even though it’s just here as an idea, a concept, with an excerpt from David Dabydeen’s poem Turner next to the repro. That’s because this exhibition presents Turner as a passionate and engaged painter of modern life. It shows how alive he was to the liberations and oppressions of his revolutionary age. Born in London in 1775, into a world ruled by aristocrats and monarchs where the horse was the fastest thing on earth, Turner lived to see the coming of trains, steamships, political reform and photography – and the abolition of the slave trade. In 1781, when Turner was six, the captain of the Zong, a Liverpool slaving ship, ordered 133 of the commodified humans he was taking from Africa to Jamaica to be thrown overboard because, in the words of a contemporary account that Turner’s title echoes, “the dead and dying slaves would have been a dead loss to the owners”. Nearly 60 years later, Turner resurrected this crime against humanity in a painting that harrows the soul with its bloody sky and flesh-filled sea. By then Britain’s slave trade was in the past, best forgotten – but not by Turner. The critic Ruskin, who owned this painting, got so upset looking at what he called “the guilty ship” that even though he recognised it as Turner’s supreme achievement, he sold it abroad. It tells a truth the British find hard to look at – then as now. Why was Turner able to visualise this horror? Because he was, as Ruskin called him, a Modern Painter. He adores the modern world in a way no one can today. A label reminds us that the smoke rising in dark grey majesty from river steamers in his c1835-40 canvas The Thames Above Waterloo Bridge is full of catastrophic carbon. But, for Turner, that smoke is sublime, a blue-tinged shadow sculpted against white mists. Turner loves steam and smoke for the chance they give him to swish wet colours in new ways. I found myself sinking, falling into Snow Storm – Steam Boat Off a Harbour’s Mouth, the vertiginous spiral of whites and blacks he claimed to have painted after lashing himself to a mast in a storm. Scholars can’t trace the boat on which he claimed it happened, but, as Ruskin insisted, it is a higher truth Turner paints. If you stand in front of this corkscrewing vortex of spume you can sense yourself spinning. Turner plunges you into a world with no solid foundations, on a ship that’s foundering. In the room dominated by the non-appearance of the Slave Ship hangs one of the weirdest Turners I have ever seen. A Disaster at Sea is thought to depict a real life tragedy that mirrors the criminality of the Zong. In 1833 a ship called the Amphitrite was wrecked off Boulogne while transporting 108 women prisoners and 12 children to the penal colony in Australia. Turner paints it as his answer to Géricault‘s Raft of the Medusa. But it’s also an erotic fantasy. Turner, to the consternation of his executor Ruskin, loved to draw and paint naked women. Here he creates a tangle of nude bodies clinging together in the slavering foamy sea – a sexy shipwreck. It’s in colossally bad taste, and unforgettable. There are so many painterly thrills in this exhibition. I was criminally tempted to touch the surfaces, to feel those ripples and troughs of paint. In Turner’s staggering, almost abstract scenes of whaling in the Arctic, blinding white surfaces are scarred and cut as if he has been carving them with a knife. This artistic radicalism is what enabled Turner to paint the Slave Ship – to imagine a historical event as if he was there. Its real meaning is revealed in the most unexpected way. I’d never noticed before how similar the Slave Ship is to his beloved masterpiece, The Fighting Temeraire, lent by the National Gallery. Both are burnished by his most heightened colours. Both depict an era that has gone. The Fighting Temeraire is a pale ghost ship pulled by a brassy steamboat: one of the last survivors of the Battle of Trafalgar being towed to oblivion. But Turner demands we remember it, with national pride. In the Slave Ship, he uses the same genius to preserve the most shameful of British memories.