If a job - in this case, to write another biography of Harold Nicolson - is worth doing at all, it is worth doing well. Being a professor of international relations, Norman Rose has the most necessary qualification of all for the task: a professional understanding of foreign affairs - something that Nicolson's previous biographer, the diarist and aesthete James Lees-Milne, lacked. For the first time, the emphasis is placed not on Nicolson the writer, politician and cuckolded husband of Vita Sackville-West, but on Nicolson the brilliant young diplomat who, by the early 1920s, was already on the way to succeeding his father as permanent head of the Foreign Office. Nicolson never shone as a politician - he once threw in his lot with Oswald Mosley - and never excelled as a writer. However, he had the ear of two prime ministers, Arthur Balfour and David Lloyd George, and two foreign ministers, Curzon and Austen Chamberlain, and for a brief period, around the time of the First World War, he played a distinguished role in world affairs.
When the old Austro-Hungarian em-peror Franz Josef died in November 1916, his successor, Karl, put out feelers for a separate peace between the crumbling empire and the Allies. Nicolson, Rose tells us, was apparently a lone voice at the Foreign Office in favour. Against everybody's views, he suggested peace with Austria. He was also an early backer of the Zionist cause - in fact Balfour's "staunchest adviser". It would, he argued, restore to the Jews their dignity, that "corporate national confidence" they so clearly lacked. Palestine would be "a nice place in which to collect all the Jews of the world as Butlins collects the noisy holiday-makers". No wonder Balfour considered Nicolson "irreplaceable".
Rose is an accomplished guide to this serious part of his subject's life. He makes excellent use of Nicolson's own account, which never failed to squeeze every drop of hilarity out of matters of peace and war, life and death. Rose tells the story of how in 1914, on the eve of the First World War, it fell to Nicolson to deliver a revised version of Britain's ultimatum to Prince Lichnowsky, the German ambassador in London. When he arrived at the embassy, at around 11pm, Nicolson was told that the ambassador was asleep and could not be disturbed. Having stressed the gravity of the situation, Nicolson was finally escorted to Lichnowsky's bedroom, where he found him reclining on his bed in his pyjamas.
[Lichnowsky] . . . waved Harold over to the writing table by the window where the papers lay, apparently unexamined. Harold made the exchange . . . Lichnowsky turned away from Harold, signalling that the interview had come to an end. But he was a diplomatist schooled in the old ways: "Give my best regards to your father," he entreated Harold. "I shall not in all probability see him before my departure."
Never again was Nicolson so much at the centre of affairs; these early years were the most fulfilled of his life. By making this clear, Rose helps the reader to appreciate how cruel it was of Vita (aided by her lover Virginia Woolf) to persuade Nicolson to resign from the Foreign Office in favour of what amounted to little more than a humiliating job as gossip writer for Lord Beaverbrook's London Evening Standard. From then on, his life was spent in the shadows - albeit among aristocrats and glamorous bohemians. It was weak of Nicolson to allow these Sapphic conspirators to ruin his life, but Rose demonstrates in excruciating detail how Vita left him no alternative. She refused to fulfil all her spouse-like public duties and made her wildly scandalous homosexual affairs all too public - thereby drawing attention to Nicolson's own, more discreet ones.
Rose does not judge or criticise. Given Nicolson's homosexual proclivities, in which he promiscuously and happily indulged, perhaps Vita was doing him a favour. His diplomatic career had already been put on hold after he contracted gonorrhoea in Madrid. And after spending a weekend in 1917 at Knebworth, where the guests included the painter John Lavery, the senior civil servant Edward Marsh, the diplomatists Horace Rumbold and Louis Mallet and the writer Osbert Sitwell, Nicolson suspected that he had caught another venereal infection from "one of the male guests (or servants)". Even without Vita's selfishness, his career might have come to a sticky end.
Yet this is by no means certain. As this book shows, the fate of Oscar Wilde was in those days the exception rather than the rule. Newspapers were more tolerant and discreet than they are today. Just as juries were far more unwilling to convict suspected murderers when the death penalty was still a punishment, so were newspapers less willing to expose homosexuals when they might be sent to prison for two years' hard labour. Certainly, Nicolson was upbeat on his favourite subject, agreeing with his friend Raymond Mortimer that being a homosexual was at least "better than having a bad squint or an incurable stammer". In a letter to one of his sons many years later, he wrote that homosexuality was "as if you liked oysters done in sherry: not a thing to be particularly ashamed of or particularly proud of".
Nicolson's life supplies all the ingredients for an entertaining and enlightening biography. Most of the literary, social and political giants of the 20th century, from Churchill to Proust, play brilliant cameo roles, as do the stars of the demi-monde, not to mention the gutter. Equally rich in biographical material is the strange and even slightly sinister family life - passed in the idyllic surroundings of Sissinghurst Castle, surrounded by Vita's superb garden - from which the elder son, Ben, could not wait to escape. Readers, however, have less reason to be censorious. Hitler took Nicolson seriously - his name figures prominently on the Fuhrer's list of dangerous Englishmen. Not a bad testimonial.
Peregrine Worsthorne's most recent book is In Defence of Aristocracy (HarperCollins)