In this he was influenced by the German historian Oswald Spengler’s recently published The Decline of the West (whose salient passages Byron marked with enthusiastic pencil scorings), a work which scorned the Western enslavement to classicism and the “empty figment of one linear history.”

By now Byron was becoming famous. His books, though rarely selling well, had achieved for him, in aggregate, a succes d’estime. Their reception was mixed with dissent—accusations of facetiousness and overwriting abound—but his admirers, from Waugh to Rebecca West, were prestigious. Arnold Bennett praised The Station for its urbane wit and observation, and D. H. Lawrence, reviewing it in Vogue, declared: “Athos is an old place, and Mr Byron is a young man. The combination for once is really happy.”

Byron wrote that the catalyst for his fascination with Persian art was a photograph of Gumbad-i-Kabus, the great eleventh-century tomb-tower near the Caspian Sea. An obsession with Persian brickwork followed, as he studied the works of Arthur Upham Pope, doyen of Persian art studies. By early 1933 Byron was hatching a plan for an expedition to Chinese Turkestan, today’s Xinjiang, but it was thwarted by native insurrection. So the goal became Afghanistan through Persia. At first he was to link up with an eccentric two-lorry expedition testing the use of charcoal gas instead of petrol; but he parted from it, with relief, within hours of their rendezvous in Afghanistan.

His companion instead was a friend his own age, Christopher Sykes, a Persian-speaker who had briefly been honorary attaché at the Tehran embassy, and who was engaged—unknown to Byron—in espionage. The world they were entering was in flux. In Afghanistan the ruler Nadir Shah was murdered while Byron was still in Iran, and was succeeded by his cautious and long-surviving son Zahir. In Iran, by contrast, a new dynasty, the Pahlavi, had taken power in 1925, and its first Shah was an autocratic moderniser. Byron ridiculed him in a typical anecdote:

I remarked to Christopher on the indignity of the people’s clothes: “Why does the Shah make them wear those hats?”
“Sh. You mustn’t mention the Shah out loud. Call him Mr. Smith.”
“I always call Mussolini Mr. Smith in Italy.”
“Well, Mr. Brown.”
“No, that’s Stalin’s name in Russia.”
“Mr. Jones then.”
“Jones is no good either. Hitler has to have it now that Primo de Rivera is dead. And anyhow I get confused with these ordinary names. We had better call him Marjoribanks, if we want to remember whom we mean.”
“All right. And you had better write it too, in case they confiscate your diary.”
I shall in future.

He did. Byron started the journey in high spirits. In Venice, where his book begins, his half-requited passion for Desmond Parsons, son of the fifth Earl of Rosse, was momentarily assuaged during a three-day reunion. The novelist Anthony Powell, a contemporary, called Byron “congenitally homosexual”, but his known relationships seem to have been cool or failed. Plump, short, with hooded eyes, his attraction was in his personality and conversation.

In The Road to Oxiana his humour spans every genre from quirky playlets to uproarious vignettes and nuggets of gossip. In this irreverent context the scenic descriptions glow with sudden poetry. Above all his evocations of Persian architecture are delivered with a descriptive gift which has never been surpassed: passionately attentive, lyrical, yet almost scientifically precise.