Seamus Costello

Seamus Costello (Irish: Séamus Mac Coisdealbha, 1939 – 5 October 1977) was an Irish politician. He was a leader of Official Sinn Féin and the Official Irish Republican Army and latterly of the Irish Republican Socialist Party (IRSP) and the Irish National Liberation Army (INLA).

Despite the truce, Costello was shot dead with a shotgun as he sat in his car on Northbrook Avenue, off the North Strand Road in Dublin on 5 October 1977 allegedly by a member of the Official IRA, Jim Flynn, who happened to be in the area at the time. The Official and Provisional IRAs both denied responsibility and Sinn Féin/The Workers' Party issued a statement condemning the killing. Members of an opposing INLA faction in Belfast also denied the killing. However, the INLA eventually deemed Flynn the person responsible, and he was shot dead in June 1982 in the North Strand, Dublin, very close to the spot where Costello died.

In July 1976 Costello was replaced as INLA chief-of-staff by South Londonderry man Eddy McNicholl, although he still wielded considerable influence within the movement, retaining his position as chairman of the IRSP.

He stood again in the 1974 local elections and topped the poll for the Wicklow County Council and the Bray Urban District Council.

At a meeting in the Lucan Spa Hotel near Dublin, on 8 December 1974, the Irish Republican Socialist Party was formed by republicans, socialists, and trade unionists with Costello as the Chairperson.

Costello was opposed to the 1972 ceasefire and started to clash openly with the leadership, in particular Eoin Ó Murchú. Costello was subjected to court martial in 1974. Brigid Makowski, who was called to testify at his court martial in Mornington in County Meath, remarked that "Jesus could have testified on Costello's behalf and it wouldn't have changed the verdict." He was dismissed from OSF in 1974 after the OSF leadership blocked his supporters from attending the party convention.

After the Troubles broke out in Northern Ireland in 1969, factions in both the IRA and Sinn Féin were divided over abstentionism and the left-wing faction's socialist politics. The republican movement divided into Official and Provisional movements in 1969/70, but Costello remained with the Officials, owing to a greater commitment to left-wing politics. He served as Vice-President of Official Sinn Féin and as a staff officer in the Official IRA.

After his release, Costello worked to rebuild the republican movement, beginning by building a local base of support in County Wicklow as Sinn Féin's local organiser. Costello strongly supported the movement's left-wing orientation of these years, especially its emphasis on grassroots political activism. He helped found a strong tenants' association in Bray, and also became involved with the credit union movement and various farmers' organisations. During this period, he married a Tipperary woman, Maeliosa, who also became active in the republican movement. Costello was elected to both Bray Urban District Council and Wicklow County Council in 1966.

He was arrested in Glencree, County Wicklow, in 1957 and sentenced to six months in Mountjoy Prison. On his release, he was immediately interned in the Curragh prison camp for two years.