The story is reasonably well known: Charles Dickens would even lead friends to the spot where it happened. In August 1843, Richard Dadd, a talented artist and \"one of nature\'s aristocrats\", returned from a ten-month grand tour of the Near East, where he had visited the Valley of the Kings. His father, concerned that Dadd might have caught sunstroke in Egypt, sought medical advice — which was that he should be hospitalised. In response, Dadd suggested they take a stroll in Cobham Park, the site of his childhood walks, so that he might \"unburthen\" his mind. Instead, while his father was answering a call of nature, Dadd stabbed him with a five-inch knife and declared: \"Go, and tell the great god Osiris that I have done the deed which is to set him free.\" He then fled to Calais intending to kill the emperor of Austria but was interrupted by a communication from the stars in Ursa Major to attack a fellow passenger with \"an excellent English razor\". Interviewed by a French doctor after his arrest, the hitherto sensitive and charming Dadd declared that he was the son of the Sun, into which he stared all day without blinking. The doctor suggested a course of ice-cold showers — virtually the only treatment that Dadd was to be prescribed for his condition, now understood as schizophrenia. The first person legally to be extradited from France, Dadd was sent as a \"criminal lunatic\" to the Bethlem asylum in London and then, 20 years later, to Broadmoor Hospital. He committed no further acts of violence and, aside from painting every day, showed no interest in any activity other than cricket (proof for some of the gravity of his delusions). But his paintings, as Nicholas Tromans reminds us in this excellent account of Dadd\'s life and art, are extraordinary. They have directly influenced, among others, Freddie Mercury, Octavio Paz, Angela Carter and Terry Pratchett. The Artist and the Asylum is witty, economical and encompassing. The author, building on the pioneering work of Patricia Allderidge, makes no extravagant claims and must be congratulated for his no-nonsense criticism and his brisk insights, for example into the \"coagulated complexity\" of a Dadd masterpiece such as Contradiction: Oberon and Titania (1854-58): \"It resembles a view — or rather a series of views — through a microscope, but at the same time it feels like something vast.\" What makes somebody mad? A table of the causes of insanity in 1835 included \"reading novels\". Our understanding of the brain and its relation to the history of art is still minimal. Tromans is keen to separate Dadd from, say, the type of Outsider artist encouraged and collected by the Heidelberg doctor Hans Prinzhorn. Such artists, Tromans argues, were inmates of asylums before they picked up a brush. Dadd\'s work cannot be judged according to the same canons. Nor is his art any odder than his belief in the continuity of cultures — to the end of his days, Dadd would argue that Christianity evolved naturally out of Egyptian mythology. And didn\'t the great Turner himself (whose mother was another inmate at Bethlem) declare: \"The Sun is God\"? Instead, Tromans would prefer to cast Dadd not as a baffling crackpot but as a noble and teasing visionary in the mould of William Blake. Dadd was disposed to madness as a fashionable subject before he succumbed to it; he painted portraits of Byron\'s Manfred (now lost) and also Hamlet (the scene where the prince\'s mother declares, \"Alas, he\'s mad!\"). Tromans observes that Dadd\'s iconography after he murdered his father consolidated around two themes: Shakespeare\'s fairy sequences, especially in A Midsummer Night\'s Dream, and the desert landscapes of the Near East. After he was incarcerated in Bethlem and Broadmoor, Dadd was not allowed to have women model for him. He had to draw on his memories of Egyptian female water-carriers whom he had considered, when sane, \"very capital subjects for the brush\". His audience, which had once been sizeable, shrank to the two or three superintendents who took an interest in his work. Foremost among them was George Haydon, whose mosquito collection may have inspired the gnat coachmen in another masterpiece, The Fairy Feller\'s Masterstroke (1855-64). Tantalisingly, several Dadd paintings have gone missing, although one resurfaced in 1986 during an edition of the BBC\'s Antiques Roadshow. More than likely, there are works by Dadd still out there, waiting to be discovered, waiting to dazzle us with their unique combination o the microscopic and the vast.