Among the Last Great Eccentrics : GERALD BRENAN: THE INTERIOR CASTLE; A Biography, <i> By Jonathan Gathorne-Hardy (W. W. Norton: $35; 672 pp.)</i>

Gerald Brenan has a street named after him in Spain. In the “Oxford Companion to English Literature” he gets 10 lines, little more than a footnote by that publication’s companionable standards.

To Spaniards, he holds a place not far short of De Tocqueville’s in the United States: the rare foreigner who could tell them something about themselves. Whereas in Britain, when his obituaries appeared in 1985, the news was not that he had died but that he was still alive. If almost any literate English person under 40 had been asked about him, the answer would have been a question, or several: Didn’t he write something about the Spanish Civil War? And didn’t he have something to do with Bloomsbury? And didn’t he live in a remote Spanish village and have lots of visitors?

The answer is yes. “The Spanish Labyrinth,” published four years after the Civil War ended, was the first major historical perspective on a conflict treated until then in terms of drama and ideological passion. Written with wit, lucidity and a Gibbon-like sweep--as well as a human detail earned by years of living in southern Spain--it was an inspiration to such later historians as Raymond Carr and Hugh Thomas. Circulated semi-clandestinely in Spain, it provided, until the looser later years of the Franco regime, a liberal historical continuity for Spanish scholars working under constraints.

As for Bloomsbury, Brenan was a junior member who came and went. He was not up to its high standards of rational discourse and judgment, though the elect thought he was promising, and E. .M Forster came over at teatime to inspect him. Romantically, though, he was quite at their level of carnal confusion. He had a passionate and partly physical affair--protracted kissing and writhing, mostly--with Dora Carrington, who lusted incorporeally for Lytton Strachey and slept distractedly with another Bloomsburyite, Ralph Partridge.

As for the Spanish villages, in the 1920s he spent three years or so in Yegen, a remote hamlet in the barren foothills of the Sierra Nevada. Before and after the Civil War he lived in Churriana, near Malaga, and in his last years he moved to Alhaurin, a hamlet farther up in the hills. Over the years his visitors included Bloomsburyites who arrived by donkey over the mountains, complained about the food and fleas, and boasted about their adventure for years afterward. Strachey, pale as a celery stalk under his sunshade, suffered pitifully from piles and punctuated his donkey’s amble with occasional moans of “Death!”

When Brenan was 88, the British ambassador, Sir Richard Parsons, left his Rolls down on the highway and trudged up to Alhaurin with two bottles of champagne and the order of Commander of the British Empire. After bestowing the honor and finding Brenan near blind and too tired to talk, he read Browning to him. Later, unaware that his visitor had been holding a book, the writer remarked to a friend that “the range of culture in general and especially the knowledge of poetry now thought necessary for senior diplomatic posts was quite amazing.”

All this comes from Jonathan Gathorne-Hardy’s biography, whose 672 pages, with four appendixes and lavish footnotes, may seem out of proportion to those 10 lines in the Oxford. In truth, it is a little long, particularly in the middle section where Brenan is spending the wartime years in England and doing a good deal of visiting himself.

Yet it is a remarkable book. The author portrays one of the last in a generation of great English eccentrics, and he has done it with a perception, a passion and sometimes an eccentricity that matches his subject. Gathorne-Hardy made friends with Brenan in his later years, did him various services and at one point was made an executor. At times his book has the feel of a memoir as much as a biography.

Brenan was born in 1894 to a retired major who was a Blimpish martinet and deaf to boot, and to a dreamy, timorous mother. He went through one of those oddly fruitful psychic cripplings that were a literary staple of turn-of-the-century English childhoods.

Drawing on Brenan’s books, published memoirs and a wealth of unpublished correspondence, Gathorne-Hardy gives a vivid picture of Brenan at all ages. An adolescent aesthete, he defied his father’s prescription of a military career and ran off for a six-month walking tour of Europe. He disguised himself as a gas repairman to make his escape and, with an older friend, wandered through France and Italy with a cart, a donkey, cooking pots and six volumes of Gibbon, which he read as he walked. When his companion turned back at Rijeka, Brenan pressed on, trudging penniless through a Bosnian winter and at one point fending off wolves--or perhaps a large dog--with his blue Italian umbrella.

Walking had a spiritual meaning for Brenan; apart from taking him away from his overbearing father it allowed him to assert a kind of personal sovereignty over the world and over his nerves. In his Spanish years he would hike prodigious distances, and even after his legs weakened he traveled happily by third-class railway carriage through the south of Europe and into Morocco. Frequently he had a younger female companion.

Brenan was married, more or less happily. For his wife, Gamel, a talented minor poet and novelist, things were less happy. Her husband kept falling in love with younger and younger women and telling everyone about it. He wrote to Ralph Partridge and V. S. Pritchett of his obsessive sexual passion for his own daughter, Miranda, with whom he bathed naked until she was 16. In his 70s he brought home a beautiful niece of Dora Carrington’s and tried mightily though unsuccessfully to sleep with her. After Gamel died, he brought in another young woman, Lynda Price, whom he had lined up beforehand. Her kindness and tact enabled her to convert him from a dirty old man into a great-uncle-mentor. She took care of him, and in turn he guided her reading and encouraged her luminous translations of the poet St. John of the Cross.

Gathorne-Hardy reports that Brenan was largely impotent. He estimates that his accounts of many of his numerous “affairs” were exaggerated. He takes a perhaps excessive interest in the details and rather cheers his subject on. “For a moment the heart leaps,” he writes when one young Frenchwoman climbed into Brenan’s bed.

Thinking of himself as a poet and novelist, Brenan wrote amazingly badly until he was 50 and discovered Spain. Not as a place, because he had been there since his 20s, but as a subject and as a form. He began a series of books--”Labyrinth,” “The Literature of the Spanish People” and “The Face of Spain” and “South from Granada,” two remarkable portraits of the Spanish landscape and character--that are ostensibly factual but through which poetry works all but invisibly.

From “The Literature of the Spanish People”: “Of all European literatures Spanish is the most homogeneous. The popular poetry of the village, still being made and sung today, drifts like smoke into the brains of the cultured writers.”

In “Granada,” he writes of a bird which “with its cheep cheep cheep seemed to be sewing together thin layers of silence.” And looking out to the Mediterranean at night he writes: “I never get tired of the lighthouse. It never says ‘no,’ it can only say ‘yes.’ ”

Spain liberated in Brenan a creative energy that he was never able to exercise at home. It is an odd example, perhaps, of the domestic inhibitions that allowed so many English Edwardians and Victorians to be themselves only when abroad. In the empire of English literature he was the remarkable governor of a small colonial state.