Egon Schiele, Courtauld Gallery, London

Is a revolutionary artist more effective when his radicalism becomes the new establishment, or when he remains unnerving?

The story of the 20th-century avant-garde, from Duchamp to Damien Hirst, is of shocks co-opted so quickly by museum endorsement that turbulence is tamed, sensation muted. The only modernist to whom we have not accommodated ourselves in this way is Egon Schiele.

It is not just that there is not a single Schiele in any British public gallery. It is that his raw, expressive nude portrayals of young girls, children and of himself just out of adolescence are today more, not less, disturbing than when he created them in Vienna between 1910 and 1918. This may be why the Courtauld Gallery’s terrific new show of works on paper, Egon Schiele: The Radical Nude, is the first solo UK museum exhibition devoted to the artist.

It is a myth that Schiele was unsuccessful during his lifetime. In 1915 museums were already buying extremely provocative pieces: the gouache/watercolour stunner of a naked lesbian couple with nipples and lips highlighted in lurid red, “Two Girls Embracing”, for example, a highlight of this show, lent by the Szepmuveszeti, Budapest. By 1918, queues of collectors wanted virtuoso drawings such as the dramatically foreshortened “Woman in Boots with Raised Skirt” here, the unbroken economical black crayon line and compressed organisation, focused on a single aggressive staring eye and flash of genitals, achieved with a rushed fluency suggesting an immediate, two-minute encounter between artist and model.

We know, too, of the steady pre-1914 market for Schiele’s tremulously explicit drawings and watercolours of his fragile-looking young lover Wally Neuzil, distinguished by her widely-spaced eyes, generous mouth, piled-up auburn hair and willingness to adopt frank poses, legs wide open, hands lifting clothes to expose vulva and pubic hair as in “Woman with Black Stockings”. Neuzil herself delivered these to clients whose ribald remarks often reduced her to tears.

Although Schiele moaned that he “certainly didn’t feel erotic” making such drawings, the Courtauld’s excellent catalogue shows how their composition – the framing of penetrable body parts, positioning of hands in relation to genitals, striptease-like juxtaposing of fabric and flesh – derive undeniably from the pornographic photographs pervading Vienna’s visual culture, available in every coffee house, at this time. Child prostitution was also rife, and Schiele employed under-age models – skinny, waif-like, with emaciated arms and claw-like hands – for images that hover between seduction and pathos, such as “Seated Nude Girl with Pigtails”.

Another regular model was his younger sister Gerti; aged 17 and 13, the pair ran away together to Trieste, following the route of their parents’ honeymoon. In “Seated Female Nude with Raised Right Arm”, Gerti is half-aware of her blossoming sexuality, half-absorbed merely in adjusting her luxuriant hair. Was Schiele, in the city where Freud was inventing psychoanalysis, engrossed in fantasies about childhood sexuality and incest, or drawing attention to abuse, or colluding with it, or simply pushing expressive realism to its limits? Whatever he was doing, it became more troubling as, in the 20th century, we all became Freudians.

By the 1940s and 1950s there were only a handful of collectors. At the first UK exhibition, at Marlborough Gallery in 1964, Oskar Kokoschka derided its organiser Wolfgang Fischer, “So you’ve been having a show of that little crook, that pornographer”, and the Burlington Magazine said the works resembled “inspired graffiti from some public lavatory”. Collector Benedict Silverman, who a little later displayed his Schieles in his New York penthouse, told me: “No one ever said, ‘Wow!’. People would walk away in distaste. ‘How can you live with these?’ was the response.”

Are we less reticent now? In an era obsessed by underage grooming and fears of childhood under attack from internet porn, I am not sure it is possible to look at Schiele without unease. Indeed, the only parallel I can think of for a great work of art increasingly disturbing us is the fraught responses to Vladimir Nabokov’s Lolita (1955). Yet just as no writer has depicted a vulnerable 12-year-old girl more tenderly than Nabokov, so no painter ever caught the innocent/knowing, awkward/manipulative contradictions of early teenage self-presentation as delicately, heartbreakingly, as Schiele.

The drama of emerging self-identity, writer and artist acknowledged, included sexuality, its power, confusion, even tragedy – as in Schiele’s striking, subverted Madonna motif, “Woman with Homunculus”, depicting a young girl casting us a sly, sexual glance as she pulls away in horror from a deformed child attached to her back.

Schiele’s own self-confrontations between 1910 and 1913 are brilliantly orchestrated. In precarious, histrionic poses, he is by turns feverishly animated, as in the frantically scribbled limbs and musculature of the tilted, gyrating “The Dancer”, or stilted and jerky as a puppet or mime, in the Museum of Modern Art’s ravishing “Standing Male Nude with Arms Raised, Back View”.

In the nervous, jagged outlines of “Standing Man”, Schiele is a bony beggar, rags falling off his back; the cadaverous “Self-portrait, Nude”, in muddy rust-browns and ochres, evokes flesh fallen away; arms and legs are truncated. “Nude Self-portrait in Grey with Open Mouth”, where contorted features and parted lips recall the despairing expression of Munch’s “The Scream”, takes the form of a crucified figure, the racked body a code for artistic suffering. No one had depicted the artist as ugly and decrepit before. What is staged, what authentic? This is the truth of the adolescent mind, searching, shifting, adopting extreme positions. But the formal achievement is precociously assured: deft use of colour; intensely articulated contours that make one feel viscerally flesh and sinew.

Although Schiele had an easy war – as a guard in a camp of Russian prisoners, whom he drew – he grew up after 1914; there are fewer tormented self-portraits, and the beginnings of a greater monumentality emerged. The defiantly inelegant view of buttocks and hips, huge in relation to the receding shoulders and tiny bunch of hair, in “Female Nude, Back View”, and the hunched figure carved from a cocoon of emerald and blue drapery in the complex “Crouching Woman with a Green Headscarf”, are magnificently sculptural.

Aged 28, Schiele died in the Spanish flu epidemic of 1918; his final drawings were of his pregnant, dying wife, who predeceased him by three days. Benefiting from top loans, this concentrated show of an arrested genius is among London’s best exhibitions of 2014.

‘Egon Schiele: The Radical Nude’, Courtauld Gallery, London, October 23-January 18, courtauld.ac.uk

Photographs: akg-images/Museum of Fine Arts, Budapest; Leopold Museum/ Manfred Thumberger; Fine Art Images/Heritage Images/Getty Images