The Dublin-born cardinal who barred Mary McAleese from the Vatican has become one of the most important men in the Catholic Church.
Pope Francis has appointed Cardinal Kevin Farrell to the role of camerlengo, who keeps the Church running between the death of one pope and election of a new one.
It's the highest office in Vatican to which an Irish priest has ever been appointed.
Cardinal Farrell, who grew up in Dublin, oversaw the World Meeting of Families here last August and is prefect of the Vatican Department for Laity, Family and Life.
The office of camerlengo has been vacant since last July.
Last year, Cardinal Farrell (71) landed himself in controversy when he refused to grant permission to former President Ms McAleese and two other women to speak at a conference in the Vatican on International Women's Day.
The event was moved and Ms McAleese blasted the Catholic Church in her address as a "primary global carrier of the toxic virus of misogyny" and "a male bastion of patronising platitudes".
His new duties as camerlengo will involve overseeing preparations for a papal conclave to elect a new pope, in addition to the administration of the Holy See during the period known as the 'sede vacante' between the death of a pope and election of a new one.
When Pope Francis was elected in 2013, it was the Cardinal Tauran who announced it from the Vatican balcony the words, "Habemus Papam: We have a Pope".
Cardinal Farrell left Ireland when he was 16 and joined the controversial Legion of Christ, which has been marred by scandals relating to its now deceased Mexican founder.
Ordained a priest in 1978, Farrell later left the Legion for the US Archdiocese of Washington. In 2002, he became an auxiliary bishop of Washington, serving as vicar general and adviser to then-Cardinal Theodore McCarrick.
McCarrick has recently been stripped of his office following allegations of abuse of minors and seminarians. But Cardinal Farrell has denied knowing anything about McCarrick's behaviour and said the allegations relate to McCarrick's time in New Jersey.
In 2007, Farrell was appointed Bishop of Dallas.
Pope Francis made him a cardinal in November 2016.
He is the highest-ranking Irishman in the Vatican and stood by Pope Francis in the face of conservative efforts to undermine the pontiff.
His brother Brian is also a bishop and serves as secretary of the Pontifical Council for Promoting Christian Unity.
Born in Drimnagh, Dublin, in 1947 into a committed Catholic family, Farrell was one of four boys. His father worked in the Player Wills tobacco factory.