Although he used the Gaelicised version of name in later life, Mac Stíofáin was born John Edward Drayton Stephenson in Leytonstone, London, in 1928.

On 25 July 1953, Mac Stíofáin took part in an IRA arms raid on the armoury of the Officers' Training Corps at Felsted School in Essex.

The police seized the van carrying the stolen weapons some hours later, due to it being so overloaded that it was going at about 20 mph on the Braintree bypass with a queue of traffic behind it.

[4] Upon being granted parole in 1959, Mac Stíofáin went to the Republic of Ireland with his wife and young family and settled in Dublin, and later Navan, and became known under the Irish version of his name.

Appointed IRA Director of Intelligence in 1966, Mac Stíofáin continued to voice his opposition to the Goulding line and was gaining support among members.

Despite his hostility to the left-wing direction, he was prominent in agitations in Midleton against ground-rent landlordism, the Dublin Housing Action Committee and against foreign buy-outs of Irish farmland in County Meath, where he moved with his family in 1966.

[citation needed] He was a devout Catholic, and was infuriated by an article in the United Irishman, by Roy Johnston, condemning the reciting of the Rosary at republican commemorations as "sectarian".

At this, the Marxist leadership of Sinn Féin failed to attain the prerequisite two-thirds majority necessary to overturn the party's constitutional opposition to "partitionist" assemblies.

This was despite the disbandment of pro-abstentionist branches and district committees, such as the 1966 dissolution of the entire North Kerry Comhairle Ceantair of Sinn Féin, embracing 13 cumainn (branches) and 250 members and including three local councillors and expulsion of leading figures such as May Daly (sister of Charlie Daly, executed at Drumboe, Donegal, in 1923), John Joe Rice, Sinn Féin TD from 1957 to 1961 and John Joe Sheehy, veteran republican and Kerry footballer.

The split also ended Mac Stíofáin's friendship with Cathal Goulding, who went on to serve as chief of staff of the rival Official IRA.

Other IRA leaders in attendance were Dáithí Ó Conaill, Martin McGuinness, Gerry Adams, Seamus Twomey and Ivor Bell.

In his memoirs, Mac Stíofáin described the operation as "a concerted sabotage offensive" intended to demonstrate the IRA was capable of planting a large number of bombs at once.

Political fallout arising from the interview was considerable and some days later, Fianna Fáil minister Gerry Collins sacked the entire RTÉ authority.

[10][11][12] Following standard procedures, Mac Stíofáin lost his rank upon arrest and he never again regained his influence within the IRA after his release in April 1973.

[citation needed] After he was sidelined, Mac Stíofáin began working as a distribution manager and part-time columnist with the Sinn Féin newspaper, An Phoblacht, in the late 1970s.

He resigned from the party in 1982 after a disagreement about strategy at the Ard Fheis, when a majority opposed the Éire Nua policy, which envisaged the setting up of regional governments in each of the traditional four Provinces of Ireland.

In her oration, Ita Ní Chionnaigh of Conradh na Gaeilge, whose flag draped the coffin, lambasted Mac Stíofáin's "character assassination" by the "gutter press" and praised him as a man who had been "interested in the rights of men and women and people anywhere in the world who were oppressed, including Irish speakers in Ireland, who are also oppressed".