David Neligan, intelligence agent, police detective and superintendent known by his sobriquet “The Spy in the Castle,” dies on October 6, 1983, at St. Vincent’s Hospital in Dublin. He is a figure involved in the Irish War of Independence (1919–21) and subsequently becomes Director of Military Intelligence for the Irish Army after the Irish Civil War (1922–23).

Neligan is born on October 14, 1899, at Templeglantine, County Limerick, where his parents, David and Elizabeth Neligan (née Mullan), are primary school teachers. He is an accomplished hurler with his local Templeglantine GAA club. In 1917, he joins the Irish Volunteers, the military organisation established in 1913 by Irish nationalists.

Against his father’s wishes, Neligan joins the Dublin Metropolitan Police (DMP) – also in 1917. Picking up travel documentation from the local Royal Irish Constabulary barracks, he declines a suggestion that he enlist in this armed rural force. After service as a uniformed constable with the DMP, he is promoted to Detective and transferred into the Department’s widely hated counterintelligence and anti-political-subversion unit, the G Division, in 1919. In May 1920, his elder brother Maurice (1895–1920), an Irish Republican Army (IRA) member and friend of Michael Collins, persuades him to resign from the DMP.

After his resignation, Neligan returns to his native County Limerick with the intention of joining the Limerick IRA. Shortly afterward, Maurice is killed in a motorcycle accident, near their home in Templeglantine. In the meantime, Neligan also receives word from a family friend that Michael Collins wishes to meet with him in Dublin. Collins is outraged that Neligan has been allowed to resign and persuades him to rejoin the DMP as a mole for the intelligence wing of the IRA. Along with Detectives Eamon Broy and James McNamara, Neligan acts as a highly valuable agent for Collins and passes on reams of vital information. He leaks documents about the relative importance of police and military personnel and also warns insurgents of upcoming raids and ambushes. There are unconfirmed rumors that Neligan might be a double agent working for British interests.

In 1921, Collins orders Neligan to let himself be recruited into MI5 and he uses the opportunity to memorise their passwords and the identities of their agents. All of this is passed on to Collins. After Broy and McNamara are dismissed in 1921, Neligan becomes Collins’ most important mole inside Dublin Castle.

On the outbreak of the Irish Civil War in June 1922, Neligan joins the Irish Army in Islandbridge Barracks with the rank of Commandant, and is attached to the Dublin Guard. He is involved in the seaborne assault on Fenit, County Kerry, and spends the remainder of the war serving as a military intelligence officer operating between Ballymullen Barracks, Tralee and Killarney. He is involved in atrocities alongside Paddy Daly including the Ballyseedy massacre, mock executions and the torture of prisoners using crowbars and is sometimes referred to as the “Butcher of Kerry.” In 1923, he is posted to Dublin, where he is promoted to Colonel and succeeds Diarmuid O’Hegarty as the Irish Army’s Director of Military Intelligence.

In 1924, Neligan hands over his post to the youthful Colonel Michael Joe Costello and takes command of the DMP, which still continues as a force separate from the newly established Garda Síochána, with the rank of Chief Superintendent. The next year he transfers to the Garda when the two police forces are amalgamated, and is instrumental in the foundation of the Garda Special Branch. When Éamon de Valera becomes head of government in 1932, his republican followers demand Neligan’s dismissal. Instead, Neligan is transferred to an equivalent post in the Irish Civil Service. In June 1935, he is married to fellow civil servant Sheila Maeve Rogan. They have one son and three daughters, and reside at 15 St. Helen’s Road, Booterstown, Dublin.

Neligan draws pensions from the DMP, the British MI5, the Garda Síochána and the Irish Civil Service. He also receives an “Old IRA” pension through the Department of Defence.