Henry Hitchings, the Evening Standard's theatre critic, has been suffering from a mild case of anglophilia for some years. The first symptoms appeared with his study of Dr Johnson's dictionary, followed by two well-received books on the by-ways of the English language (The Secret Life of Words and The Language Wars). Now, he has succumbed to a full-blown case of anglomania, a study of English social behaviour through the ages whose title  Sorry!  suggests that he knows his affliction is both contagious and untreatable.

Any treatment, indeed, might be more dangerous than the cure. Hitchings's subtitle, "The English and Their Manners", indicates that he has also contracted a virulent side-effect, the agonies of the "British" question. The catalogue of commentarians who have been driven to the edge of insanity by this topic is long and distinguished. George Orwell, no less, grappled with it in his 1941 essay "The Lion and the Unicorn". Orwell noted that "we call our islands by no less than six different names", concluding with a celebration of "muddle". Hitchings, defining the territory of his investigation as best he can, acknowledges this historical difficulty, but declares that "English" rather than "British" manners acknowledge "something visceral".

Intestines, however, are also slippery. Some years ago, the Times sponsored a campaign for a British motto to rival France's Liberté, égalité, fraternité. All hell broke loose. Readers' suggestions included "Dipso, fatso, bingo, asbo, Tesco", closely followed by "No motto please, we're British". With this subject, a raised eyebrow can be as meaningful as a national mission statement.

The English have never ceased to find themselves, and the complexities of their island inheritance, fascinating. The question of "Englishness" has been a literary genre at least since Daniel Defoe made his tour of Great Britain in 1724-27. The best parts of Sorry! are when Hitchings re-examines the English "manners" of, for example, Samuel Pepys, Lord Chesterfield, who invented "etiquette", Edmund Burke, or Fanny Trollope (Anthony's mother) and her entertaining strictures about the vulgarity and self-belief of Americans.

The past is another country. As his exposition of English manners, and why we behave the way we do, approaches the present day, the rigour of Hitchings's absorbing analysis starts to break down as he becomes distracted by myriad contemporary issues and concerns, ranging from telephone etiquette (mobiles at the dinner table?), to supermarket manners (ogling a neighbour's shopping trolley). Hitchings the journalist moves his centre of gravity from the library to the field. His research becomes impressionistic and personal (a cafe in the West Midlands; a restaurant in Egypt; childhood memories from the 1970s and 80s; vox pops with young people). Hunting a moving target becomes a game of pin the tail on the donkey.

The paradox of English life is that ours is a small-c conservative, broadly democratic society founded on chaos, privilege and snobbery. Our political class emerged from the mother of all invasions by a foreign power. Our national church was created by a royal divorce case. Our famous monarchy derives from regicide and civil war. As an insular society, Britain's public face is often provincial, though its history is uniquely global. The English, in other words, are a complicated people whose "manners" can be simultaneously coarse and sophisticated, both staggeringly rude as well as astoundingly polite. Everything one says about them is true  and so is its opposite. Reconciling a long history of disruptive, sometimes thrilling, social expression with a scholarly appetite for themes will always be problematic for the historian. Hitchings has made a bold, entertaining, and often imaginative, assault on a fundamentally impossible subject. Perhaps in writing Sorry! he will have found a cure for his affliction.

One suspects that a man who writes a book about manners is in fact a seething, mad-eyed malcontent, and there are certainly moments in Sorry! The English and Their Manners when Henry Hitchings begins to bubble with anger and disquiet, eyes a-popping, mouth a-frothing, fingers feverishly scratching at the sacred cows and filthy pigs of contemporary culture. "You know how that looks and feels," he insists at one point: "the shared gawps of distress as Trendster McFuckpig blurts once again into his tiny electronic conch."

Hitchings's little fits and rages, however, are more often caused by those who take too simplistic a view of  the decline of modern manners, rather than by the jostling, beheadphoned, Pringles-munching, onesie-wearing loudmouth barbarian hordes. "I dispute the claim that manners are in decline across the board," Hitchings concludes, preferring instead the idea that "new social relationships entail new social codes", and thus manners today might be understood to be "more complex than ever before". This is not a book likely to be serialised in the Daily Mail.

Hitchings is quite an enigma. A writer of apparently limitless learning and intelligence, who writes works of scholarship masquerading as popular narrative non-fiction, he somehow manages to combine what must be marathon stints at the library with a full-time day and night-job as theatre critic of the London Evening Standard. He files a review most days and knocks out a summa every couple of years: the man is something else. Though exactly who or what is not entirely clear.

His first book, Dr Johnson's Dictionary (2005), was a work of such vigour and verve that it might have impressed the great multi-tasking Doctor himself; The Secret Life of Words (2008) was a history of the English language that seemed to leave no etymological stone unturned; and The Language Wars: A History of Proper English (2011) waded confidently into a vicious battle that has been going on for centuries with no signs of ceasing. Now, in Sorry!, a book as diverting and wide-ranging as ever, the footnotes and bibliography alone would put the average PhD student to shame.

Perhaps a key to understanding Hitchings's width and heft comes in his Who's Afraid of Jane Austen? How To Really Talk About Books You Haven't Read (2008), a guide to bluffing your way through conversations about great literature. In this most curious of his curious books, Hitchings recommends various shortcuts to pretend knowledge, including skimreading, waffling and avoiding the genuinely learned. Such techniques may explain how in Sorry! he's able so confidently to cover the history of courtesy, civility, etiquette, privacy, hat-tipping, kissing, hypocrisy, names, name-calling, table manners, the fascinating usage and abusage of the word "sprezzatura", and the rituals of bereavement. Who's to challenge his knowledge and authority in all of these areas?

And yet there is clearly nothing counterfeit about any of Hitchings's research. If anything, it's a kind of restless, wandering, burrowing through history and ideas that results not so much in an argument as in a demonstration of its own endless curiosity. If one begins occasionally to become indifferent to its shambling charms, it's perhaps because we have become inured to what another great odd, unpredictable intelligencer, Geoff Dyer, in Zona (2012)  his great looping book about another great looper, Andrei Tarkovsky  calls moron-time (in which nothing can last for longer than two seconds). We are too accustomed to art and literature that moves at the speed of Speed, with all of its predictable knock-out punches, take-downs and Robert McKee-style story shapes.

Hitchings acknowledges at the outset that a global history of manners would necessarily take in Confucius, Cicero, the Talmud, the Islamic code of adab, and goodness knows what else, so he wisely restricts himself to the English and starts with the medieval. "Let's for a moment project ourselves into this world. If you live in 13th-century England, your home is draughty and smoky ... you will be obliged to slumber on a clay floor strewn with rushes that have become ingrained with filth ... You may also share your bed with a stranger. Inhibitions are low, which is in some ways a good thing, but you see an awful lot of other people's dirty, blemished bodies. You blow your nose directly into your hand."

Mannerly behaviour in England, according to Hitchings, emerges from the moral teaching of the Christian church, develops in the monasteries, spreads throughout society through the dissemination of books and pamphlets, and gradually becomes codified over the course of hundreds of years, until finally we're all familiar with certain "acts or gestures of avoidance and restraint" that signify good behaviour  like, not blowing your nose in your hand. This at least is the chronology. More interesting are the insights along the way and where Hitchings ends up: "the ability to evaluate and regulate the effects we have on other people is part of a fine awareness of our selves. If we stop thinking about those effects, if we stop caring, we are not expressing the freedom and wonder of our selves, but limiting them. If we do not control our desires, they control us." This surprisingly firm, high-toned conclusion, proceeded as it is by pageon-page of learned meanderings and musings, reveals finally the kind of writer Hitchings really is: an overseer, guardian, wise man, guide. The Right Reverend Henry Hitchings: scholar bishop.

Ian Sansom's Paper: An Elegy is published by Fourth Estate.