But in order to write, he fled Dublin for London in 1876. A sliver short of his majority, he was no headstrong runaway. Indeed Mrs Shaw had moved to London four years earlier with her eccentric music teacher. Here, is the worst of all exiles – exile within the mother tongue – the young GBS embarked on a thankless sequence of novels. Balancing production with consumption, he also read voraciously in the British Museum where he began the ingenious dialectical exercise of interpreting Wagner in Marxist terms. The fiction sank without trace. In defiance of his natural shyness, Shaw joined the Fabian Society in 1884 and began the lifelong task of educating himself in public. For six years (1897–1903), he served as a local councillor in the London borough of St Pancras. Yet Shaw’s socialism was a middle-class affair, tempered by Irish contempt for class.

By this time, the dramatist had burst out of the novelist’s chrysalis. His first play was Widowers’ Houses, produced in London in 1892 with slum landlordism as its theme. This was also the first of the unpleasant plays, and The Philanderer and Mrs Warren’s Profession followed quickly. Shaw deemed himself a hit, but who or what was he hitting? The unpleasantness of the new drama did not lie in its ‘social problem’ aspect, for the English theatregoer was familiar with stock complaints about asylums and wicked uncles. Shaw got closer, as only a chameleon foreigner could: his topic was hypocrisy, he assaulted his audiences, not the national conscience. The national conscience was a convenient myth, behind which individuals could hide.

In my experience, the laughter which breaks out in an audience during the performance of a play by Shaw always has its nervous quality. There is amusement but also unease. His wit unsettles us. Some people may draw comfort from the hand-me-down explanation that the Irish are witty whereas the English are humorous. But this does not work for the group of four plays published in 1898 as the pleasant companions to Mrs Warren and Co. It’s the word – ‘pleasant’ – not one we associate with Shaw, and his use of it stirs up that unease again. We laugh nervously.

On the first night of Arms and the Man in 1894, there was much confusion in the theatre. The pit and gallery began to laugh, with only some loyal Fabians desisting. Then the audience discovered that the play was mocking them; its mock-melodramatic opening had turned into disconcerting farce. Silence surrounded the customary call for the author to address his first pleasant audience. When someone started to boo, Shaw declared his sympathy with him. Theatre had begun to reverse generations of conventional expectation, and Shaw was its agent provocateur. W. B. Yeats was hardly a typical member of the public, but his reaction conveys the degree of anxiety generated by the New Man: ‘Presently I had a nightmare that I was haunted by a sewing-machine, that clicked and shone, but the incredible thing was that the machine smiled, smiled perpetually.’

The implication that Shaw was mechanical intelligence as opposed to organic artifice ran deep among his enemies, many of whom – as both Wilde and Yeats testified – relied on his ability to hit the philistines for six. He seemed prepared for the twentieth century. Of the three, he alone looked to the future without apprehension.