Telling the story of Sir Roger Casement’s life is a challenge for any biographer. In the land of his birth, he is remembered as a national hero. His remains lie in the Glasnevin Cemetery in Dublin beside the graves of Daniel O’Connell and Charles Stewart Parnell. He is there because he was hanged in Pentonville Prison in August 1916 as one of the leaders of the Easter Rising. The awkward fact that Casement had become opposed to the Rising and had tried to prevent it does not fit either the heroic Irish narrative of his life or the official English account of the wartime traitor who died on the gallows.

Casement landed near Tralee, knowing that the rebellion was doomed to failure and hoping to stop it

Taken on its own terms the armed uprising in Dublin on Easter Monday 1916 was a catastrophic failure. Since there were on that morning 150,000 Irishmen serving with the British forces in France, widespread popular support was unlikely to be available. Many of the 1,550 volunteers who took part were convinced that they would be supported by the landing of German troops and artillery. By the end of the week when the rebels surrendered, large parts of central Dublin had been destroyed by shelling; 450 Dubliners had died and a further 2,600 civilians had been wounded. Fifteen of the rebel leaders were promptly court-martialled and shot.

Casement had been principally responsible for the hopes of German intervention since he had spent the previous two years in Berlin, vainly attempting to recruit volunteers from the ranks of Irish prisoners of war. He was landed near Tralee, in the south-west, from a German submarine on Good Friday, knowing that the rebellion was doomed to failure and hoping to stop it. Instead, he was arrested and taken to London, where he arrived the day before the uprising broke out. He was tried for treason by the High Court in the Strand in June and executed six weeks later.

By that time it was becoming evident that the Easter ‘catastrophe’ and its brutal aftermath were to have long-term political consequences. The martyrdom of those who had died for their country ensured that the rising was transformed from a fiasco into a potent national symbol. The dream of Home Rule – dating back to the days of Gladstone, promised by Asquith’s pre-war government, backed in Westminster by John Redmond’s Irish Parliamentary party and widely supported in Ireland – was dead.

Casement was a strikingly handsome man with a gentle manner and unusual physical strength. He was born in Dublin in 1864.  On leaving school, aged 15, and already an orphan, he was sent to live with an aunt in Liverpool where he started adult life as a clerk in the Elder Dempster shipping line. This in turn led to him travelling out to the Congo, aged 19, where he was employed by the newly established International African Association as an overseer of the labourers who were constructing a railway from the Atlantic coast along the Congo river to the point where it became a navigable high road into the interior.

The young man’s exceptional competence led to a British consular appointment and he served for most of his adult life in the Foreign Office as a loyal servant of the Empire. It was in Africa that he accomplished the first great achievement of his life, exposing the brutal enslavement of native labourers by the European overseers harvesting rubber, and huge profits, for King Leopold of the Belgians in the Congo. His official report eventually led to the king being forced to cede his vast domains to the Belgian state and made Casement an international hero. He repeated the feat in Peru in the Amazon rain forest in 1910. For these exploits he was first awarded the CMG and then knighted in King George V’s coronation honours.

In Broken Archangel, the latest in a long line of biographies (there are 11 previous life studies in the list of sources), Roland Philipps ends the first half of his account of Casement’s life in 1914; in the second half of the book he covers the final two years. For many biographers the apparently abrupt switch in Casement’s loyalties from the British crown to Irish nationalism remains mysterious. But Casement’s growing commitment to Ireland is traced by Phillips over a decade, and explained as an attempt to resolve his own confused feelings of identity. He was ‘an Irishman in an imperial Foreign Office, an Englishman… awarded the South African Medal by the Queen’. He was also a Christian who was uncertain as to whether he was Catholic or Protestant – as a child his mother may have baptised him into both denominations – and he was a homosexual in an age when expressing his sexuality was a shameful and criminal offence. Joseph Conrad, who first encountered Casement in the Congo, and admired him, said that his emotions generally governed his intelligence.

Casement kept a detailed record of his very private life in what became known as the ‘Black Diaries’. Philipps quotes repeatedly from these diaries, which may illustrate the poverty of Casement’s emotional life – largely limited to a succession of brief encounters with male strangers, not always adults. By the time Casement’s trial opened in June 1916, the ‘Black Diaries’ had been discovered and were used by the Home Office to destroy his good name. The attorney general F.E. Smith played a leading role in that destruction, and his bullying hypocrisy became a notable feature of the trial. Having first blackened his victim’s reputation, and then led for the prosecution, Smith administered the coup de grâce by refusing permission for Casement to make a final appeal to the House of Lords.

Smith, of course, had personal experience of treason, having been among the first to run guns into Ireland in 1912 to arm a carefully planned Ulster Unionist rebellion. Casement at that time had described the future attorney general as ‘a badly-trained bloodhound, sniffing at Irish blood’.

On the day before his execution Casement asked the Pentonville Prison chaplain to receive him into the Catholic Church. The chaplain referred this request to the Archbishop of Westminster, Cardinal Bourne, who ruled that Casement must first sign an apology for the ‘public or private’ scandal he had caused. Casement, in an act of extraordinary moral courage, refused to sign. The chaplain heard his confession and received him anyway.