Patrick O’Brian, author of the AubreyMaturin naval saga of the Napoleonic wars, has been variously described as “Jane Austen sur mer”, “better by a long sea mile” than the master of naval yarns, C S Forester, “an author I’d walk the plank for” - and, most tellingly, “the best writer you’ve never heard of”.

The saga has enjoyed a faithful following since the first book appeared in 1969 - yet only recently has it begun to attract serious critical attention. But then Moby Dick was hardly noticed until Herman Melville had been dead for 30 years.

O’Brian, now 82, has not quite suffered that fate. In 1995 he was the first to receive the Heywood Hill prize for lifetime contribution to literature, and he has been awarded a CBE. A S Byatt and Iris Murdoch are among his admirers (he is said to be as popular with women as with men) and the British Library recently published a collection of critical appreciations and a bibliography. Other works include a much-praised biography of Picasso, whom he knew, and another of Sir Joseph Banks, the naturalist who went with Captain James Cook to put the botany into Botany Bay. It was O’Brian who translated most of Simone de Beauvoir’s later works from French, as well as Papillon, the memoirs of Henri Charri re, the murderer who escaped from Devil’s Island.

The AubreyMaturin series, now numbering 18 volumes with the publication earlier this month of The Yellow Admiral, forms the continuing and compelling chronicle of a friendship spanning 15 years - a partnership incomparable in literature between two dissimilar but equally well-developed characters.

Captain Jack Aubrey RN is a study in the leadership of men pressed together in perilous circumstances. The red-blooded Aubrey seems the antithesis in many ways of the priggish Hornblower. Bluff, courageous and English as roast beef - when beef was still considered safe to eat even after several seasons salted below decks in oak barrels - Aubrey is the master of wind, tide and tactics afloat but a fool with women, money and his own political interests ashore. Between voyages he is really happy only when athwart his horse.

His “particular friend”, Stephen Maturin, is ostensibly a physician, sought-after in society, who signs on to the relatively lowly position of ship’s surgeon in pursuit of his passion for natural philosophy. In fact, he is also a highly valued intelligence agent - for which his post provides the perfect cover. The need to insert agent Maturin into various theatres of war also provides O’Brian with the excuse for Aubrey’s endless assignments to adventure.

Maturin is moody and mysterious; half-Irish, half-Catalan; Catholic (at a time when that was still a disqualification); devoted to life and liberty but deadly in a duel, an accomplished assassin when necessary and not above dissecting his victims in the interests of anatomical research. “An English spleen at last, the most famous of them all,” is the epitaph of one sordid traitor who dogs the seafarers through several episodes.

O’Brian closely guards his privacy, regarding his books as “the only legitimate objects of curiosity”. But comparison of his physique, experience and passions in life with his descriptions of Maturin leave little doubt on whom he draws for one of his characters. O’Brian is a naturalist, is Anglo-Irish, worked for British Intelligence in the Second World War and has lived in French Catalonia since 1949. Like the creator of Long John Silver, for much of his childhood he was bedridden and sought solace in books. After sea air was prescribed for his condition, O’Brian soon became a competent seaman, accompanying friends on ocean-going voyages.

He began writing before the war: “It never occurred to me to do anything else.” Years of research for a book on St Isidore of Seville and the western bestiary were destroyed in the London Blitz. But he had established the habit of painstaking research that was to make him the master of period. After the war came a volume of short stories and a first novel, Testimonies (recently reissued). Testimonies is set in Wales, where O’Brian and his wife, the former Countess Tolstoy, lived briefly before the lure of sun and wine drew them south. It is along the Catalan coast of the Mediterranean in 1800 that the action of the first AubreyMaturin tale,Master and Commander, takes place.

When it was first published in 1969, Sir Frances Chichester, recently ret-urned from his single-handed circumnavigation, called it “the best sea-story I have ever read”. The kind of recommendation, perhaps, to put off anyone who, like Maturin, hardly knows the sharp end of a boat from the blunt. But hearts of oak are not a necessary requisite for O’Brian readers. The doctor - preternaturally incapable of coming or going from a ship without getting wet and for some reason invariably wearing lead-soled boots - provides plenty of excuses for jolly tars to explain any unavoidable technicalities in simple terms.

Nevertheless, O’Brian is free of the journalistic compulsion to translate every term. So you must be content to imagine how exactly a rope might be joined in a cuntsplice and to let people die of the marthambles without being sure what it is. It hardly matters what the spirketting is about which the ship’s carpenter is perpetually wringing his hands. It is part of the poetry rather than the plot. As O’Brian put it: “Ignorance of the cross-catharpins is not necessarily fatal. Explanation of them certainly would be.”

The seed for the series was sown in an earlier book O’Brian wrote “for fun”. The Golden Ocean, published in 1956, recounts the adventures of an ingenuous Irish midshipman, Peter Palafox, who supposedly accompanies Commodore (later Admiral) George Anson on the three-year voyage round the world he began in 1740, in the course of which he took the fabulously rich (1,313,843 pieces of eight alone) Acapulco galleon. Like the Aubrey adventures, The Golden Ocean was the result of O’Brian‘s immersion in naval history and excellent contemporary sources. It has also just been reissued and, with its young hero and comparative lack of introspection, might be a better starting point for young readers than one of the AubreyMaturin books - though as T J Binyon, an O’Brian supporter for many years in The Times Literary Supplement, says: “Like the best children’s books, it can be appreciated fully only by adults.”

After The Golden Ocean, an American publisher suggested O’Brian write an adult book about the sea. Master and Commander was the result, followed by Post Captain in 1972. Soon O’Brian was to conclude that this was “the right kind of writing for a man of my sort”. As he was rapidly to learn, however, “the historical novel . . . belongs to a despised genre”.

Yet, he argues, the novel set in the past may have a time-free value. Living very much out of the world in the writing room he blasted out of the rock of his Roussillon vineyard, O’Brian says he knows little of present day London or Paris or of post-modernism or post-structuralism. “Yet I do have some comments, some observations to offer on the condition humaine that may be sound and of at least some interest, and it seems to me that they are best made in the context of a world that I know as a well as the reader does, a valid world so long as it is inhabited by human beings rather than by lay figures in period clothing. ”

The authenticity with which O’Brian laces his artifice is much admired. The literary, naval and medical scholars in the British Library appreciations pay tribute to the accuracy not just of his ships and events but also of the attitudes and manners - the social changes in British society and in the navy as the revolution in France and mutinies in the fleet increased class awareness and led to even greater brutality.

There is nothing contrived about the action either. As in The Golden Ocean, O’Brian invariably bases it on first-hand accounts of actual campaigns and battles. Aubrey’s first and defining victory - in which, vastly outnumbered and outgunned, he pitches his diminutive sloop Sophie against the might of a Spanish frigate - re-enacts shot-for-shot an exploit of Lord Cochrane. Captain Maryatt of Midshipman Easy drew on the same inspiration, having sailed with Cochrane as a midshipman.

But there is more to O’Brian than historical accuracy. “The fact is that O’Brian is one of the best writers now working in the English language, ” according to Charlton Heston. And others who have compared the creators of Hornblower and Aubrey also give O’Brian the advantage on subtlety of character, humour and irony. Heston the actor particularly appreciates O’Brian‘s ear for the nuances of English speech at the turn of the 18th century. “I have made a good part of my living sorting out the differences in accent and usage in English over the centuries and across national and regional boundaries. O’Brian does this all so effortlessly you would swear he wills himself back into the 19th century and makes notes: table talk that seems straight out of Jane Austen; fo’c‘s’le hands ashore on liberty, Admiralty Lords in solemn convocation at Whitehall - he catches it all flawlessly.”

John Bayley, Oxford’s emeritus Warton Professor of English Literature, says that in the naval-romantic novel, Forester remains unequalled for the dynamism of his narrative - “his single-ship actions are surely the best ever described” - whereas O’Brian‘s “real interest is in the ships and the crews, in naval custom, habit and routine , the daily ritual of shipboard life and the interplay of personality in the confinement of a wooden world”. His ships were as intimate as Emma’s Highbury, and Jane Austen’s naval brothers would have approved.

The comparison with Austen is frequently drawn. O’Brian acknowledges her as a model, though of course his canvas is much wider than is allowed by Austen’s domesticity. The saga, now 6,000 pages long, ranges far and wide across the oceans, reflecting the politics of the day and the era of discovery and self-improvement. Even Aubrey, rough and tough as he is, routinely takes sea temperatures around the world for Humboldt, who charted the Pacific currents, patiently grinds his own astronomical lenses and delivers modest mathematical papers at the Royal Society, where Sir Joseph Banks presides and Maturin long ago made his mark with his observations on Irish phanerogams. The entomologist head of naval intelligence is as delighted with the tropical beetles that Maturin produces for him from his handkerchief as he is with his espionage abroad.

O’Brian is said to be aiming to complete the series at 20. The Yellow Admiral is well up to standard. Though like all the books it is free standing, it is not the best place to start. Aubrey is either landbound, caught up with the social and economic repercussions of enclosure, or confined to the drudgery of the blockade. Like the reader, he chafes to be at sea roving again. Even worse, peace breaks out.

Aubrey’s dearest wish is to “hoist his flag”; to become an admiral. A yellow admiral is the nickname for a captain who achieves the necessary seniority but is passed over. Not for the first time, he is down on his luck. Friends and admirers find him occupations suited for his talents. But it is 1815 and the new year winds on. Will Bonaparte be content to languish in exile on Elba for ever?

Patrick O’Brian‘s novels include: Testimonies (first published 1952, reissued by Collins 1994); The Golden Ocean (first published 1956, reissued by Collins in 1996); Master and Commander (Collins 1970 Pounds 16.99) and The Yellow Admiral (Collins 1997 Pounds 15.99) uPatrick O’Brian: Critical Appreciations and a Bibliography, edited by A E Cunningham, is published by the British Library at Pounds 15 uOn the Internet there is a Web site devoted to Patrick O’Brian‘s works: http:www.princeton.edujoessurprise. html