The Man Who Lost His Language, by Sheila Hale

John Hale was one of the golden boys of 20th-century England. He enjoyed a carefree childhood in the Kent countryside in the Twenties, and loved his time at public school – years devoted to bird-watching, exploring French and Spanish literature, and immersing himself in the history of art. Because of the war he postponed his entry to Oxford, and at 18 became a radio operator in the Merchant Navy. He was ridiculously handsome in his officer's uniform, but managed to relish the chaste routine of life at sea, as well as the opposite pleasures of shore leave in Brooklyn, Sydney or Cape Town.

When peace came he threw himself into student life, making a name for himself as a glamorous actor. He looked so good that he was offered the male lead in The Blue Lagoon alongside Jean Simmons. But he chose history over histrionics, and became a mirthful Oxford don instead.

As an academic he was a paragon of effortless excellence. It was as if he had been born knowing all about Italian art, and he was a natural writer too. He turned out monographs and textbooks, and charmed a large public with grand lectures and urbane appearances on radio and TV. Above all he had a talent for enjoying himself – smoking, drinking, talking, laughing and joking. He was good, it seems, at absolutely everything, not least the arcane Oxfordian art of stammering self-deprecation.

In 1964 he became a foundation professor of history at Warwick, moving to London University in 1970 and becoming a formidable chair of the Trustees of the National Gallery. He was knighted in 1984, and retired four years later, immediately setting to work on his monumental masterpiece, The Civilization of Europe in the Renaissance. He said it was a hard book to write, but the manuscript, complete with hundreds of illustrations, was delivered exactly on time, in June 1992. He may have been nearly 70, but he was still a golden boy.

Exactly a month later, Professor Sir John Hale was lying flat on his back in his study, with an infantile smile on his face, and whispering a phrase that sounded like "the walls" or "the wars" or at any rate "da woahs". His wife, the American writer Sheila Hale, soon realised that he was not fooling around. His right side was paralysed, and "da woahs" was the only sound he could say. He had suffered that most bizarre of physiological cock-ups: a stroke.

Stroke is the perfect word for what it describes: a terrifying bolt from the blue, but quiet and painless too – a gentle caress from the reaper. John Hale's doctors were discouraging, but within a couple of months he was walking again, after a fashion. And he never stopped enjoying the gossip of his friends, even if all he could offer in return was "da woahs".

A few weeks into his therapy, Sheila Hale found her husband crying to himself, and she knew he wanted to die. But she talked him round, and The Man Who Lost His Language is the tough and touching record of the seven years they went on to have together (he died in 1999). She threw herself into research about the nature of strokes, and her lucid summaries of what she found out would make a rewarding book in themselves. But it gets even better when she leaves the science behind and tries to describe, as she puts it, "what it is like to be John".

The effects of strokes on language, consciousness and subjective experience are paradoxical. You might expect a general slow-down, or perhaps loss of sophisticated functions and regression to a so-called second childhood. But in fact it is more like losing random pages from a grammar book, so that some very fancy abilities are left intact while their logical supports are all swept away.

John Hale could still understand what he heard and read, or at least he followed it well enough until confronted with questions about what had happened, or where, when and to whom. If Sheila Hale is right, her husband's new world was no longer articulated in sentences expressing interlocking facts, but rather in images representing unstructured collections of objects. He could still understand everything, but in unaccustomed ways.

John Hale never got his spoken vocabulary back, but his stream of "da woahs", punctuated with an occasional "ach" or "Omygod", retained all the rhythms, colours and melodies of his old vocal style. Those who were not too worried about meaning found him a charming, courteous and hilarious conversationalist. He became a mime artist to rival Marcel Marceau, making fun of officious doctors and every other species of pompous fool. Yet he always seems to have supposed that his "da woahs" were meaningful and appropriate strings of words, and he was baffled and a little bored when his interlocutors kept turning the conversation towards walls or wars.

Once he had got used to holding a pencil in his left hand, he was able to draw neat little pictures, though his human figures always lacked their right hand. He could help the colleagues who were seeing his book through the press, by marking queries in the proofs and drawing little maps showing where they could find any books they might need to check.

He could still find his way around Twickenham, play chess, and plan journeys to strange places, and after a while he began to reconquer the art of writing, slowly spelling out the names of Renaissance painters. It is hard to imagine anything more moving than the slightly crazed messages of love that he scratched out for his wife, apparently with more effort and concentration than he used to spend on writing a whole book.

The mystery is that the huge physical insult to his brain seems to have changed everything about him except who he was. His spirit, as we might once have called it – or his "personality" if we feel we no longer can – survived the general devastation.

The Man Who Lost His Language fits into a burgeoning category that you could describe as Sick Lit. It belongs on the same shelf as Jean-Dominique Bauby describing the stroke that left him paralysed except for one eyelid, Robert McCrum on the one from which he recovered, and John Bayley's accounts of Iris Murdoch's dementia. But it outstrips them all in its loving exploration of a world which, to outsiders, seems like a landscape of unimaginable destruction, though for those who live there it is simply the setting of their lives.

A lot of us have had strokes already, or little episodes that may prefigure them, and no one can help wondering what surprises the next heartbeat may bring. Sheila Hale's acute and compassionate book makes the unknown country seem a little less desolate. As well as a compelling work of popular science, it is a luminous biographical memoir and an enthralling testament of love.

Jonathan Reé's book 'I See A Voice' is published by HarperCollins