What struck people first about the former Irish prime minister Garret FitzGerald, who has died aged 85, was his voice: a warm burr of sound spiced with the sharp clack of Dublin vowels that spilled out words in an unstoppable cascade. It mirrored the way that he thought, wrote and conducted his political and business lives.
These intertwined careers made him one of the most influential political and economic thinkers involved in the creation of modern Ireland, and of the north-south peace settlement. His most successful achievement, the Anglo-Irish agreement of 1985, provided a foundation for the 1998 Good Friday agreement and the present power-sharing administration in Northern Ireland.
FitzGerald was elected leader of his party, Fine Gael, in 1977, and was taoiseach from June 1981 to March 1982, and then December 1982 until March 1987. He served in office in alternation with Charles Haughey of Fianna Fáil, and the pair seemed to delight in tearing up each other's policies. He dealt successively, either as foreign minister (1973-77) or taoiseach, with the British prime ministers Edward Heath, Harold Wilson, James Callaghan and Margaret Thatcher.
It was Thatcher whom he found least easy, personally. She had far more instinctive sympathy with Haughey, a brash businessman from a background even more lowly than her own. Nevertheless, it was in partnership with Thatcher's government, and notably her foreign secretary Lord Carrington, that FitzGerald negotiated the Anglo-Irish agreement, which set up a joint civil service body to seek a constitutional way forward for Northern Ireland.
As taoiseach, he was criticised for disorganisation and failing to keep his team united through economically difficult years. Despite his essential warmth, his intellectual prowess made him impatient with lesser minds, and along with the constant babble of the voice went a deceptive air of happy amateurism. During the 1985 negotiations, he was alleged to have said: "It sounds great in practice, but how will it work in theory?"
He found the nitty-gritty of political intrigue tedious, but was not without skills, as evidenced in the way he cornered his cabinet members into support of the 1983-84 New Ireland Forum, promoting discussion between Fine Gael, its Labour coalition partner, Fianna Fáil and the SDLP. His strength lay in his puritanical propriety. When Ireland during the late 1990s was beset by sexual and financial scandals dating from the 1980s and involving Haughey, FitzGerald stood out like a beacon.
But the problems that beset him in office were overwhelming: a fragile majority and a difficult coalition cabinet, a global economic recession that the nascent Irish economy could not withstand, and the decades of violence in Northern Ireland that affected inward investment to the south and dominated southern politics.
Had he been able to hand relations with Britain and Northern Ireland to colleagues of his own mind, he might have concentrated more successfully on Ireland's economic problems, but his emotional commitment to the north was too strong for him to it let go. Within five years of leaving power in 1987, the groundwork he had done to attract inward investment, particularly from the US, was paying off in a boom in the "Celtic Tiger" economy, as were his reconciliation policies that led to the Good Friday agreement. But he left office a disappointed man.
Born into the easy world of Dublin's wealthy intelligentsia, FitzGerald felt at home in Britain, Europe and the US. After going to St Brigid's school, Bray, south of Dublin; Coláiste na Rinne, an Irish-language boarding school in Waterford; and Belvedere college, Dublin, he studied law at University College, Dublin.
His father, the poet Desmond FitzGerald, had in 1922 become the first foreign minister of the Irish Free State and a founder of Fine Gael. His mother was Mabel McConnell, a northern Presbyterian born in Belfast, so he had a strong background in cross-border politics, and retained links with her family. He was the most influential and frequent southern visitor to the north during the violence of the 1970s.
He believed that just as his parents had managed to be happy in spite of their contrasting backgrounds and political beliefs – taking different sides even during Ireland's civil war of the 1920s – so others could learn to live together. His deep understanding of Northern Ireland proved invaluable once the Troubles erupted in 1969, the year he was first elected to the Dáil, sitting for his home area, Dublin South-east.
FitzGerald had been admired by Seán Lemass, the Fianna Fail taoiseach who was attempting to build a relationship with the Belfast prime minister, Terence O'Neill, in the mid-1960s. Lemass tried to persuade him into Fianna Fáil, but FitzGerald, then an economics lecturer and journalist, joined Fine Gael out of loyalty to his father.
Lemass subsequently groomed Haughey, who became his son-in-law, as his successor, while FitzGerald worked to move Fine Gael to the centre left, to become the party of innovation. He recognised that the stranglehold that the Catholic church had on divorce and family law and the Irish constitutional claim to the territory of Northern Ireland were so repugnant to northern Protestants that they were insurmountable stumbling blocks to peaceful progress.
FitzGerald had already served as minister for economics and for education before being appointed to foreign affairs in 1973. He was the minister responsible throughout the Sunningdale agreement negotiations with Heath's Conservative government in Britain that year, and during the collapse of the power-sharing executive that Sunningdale created in Belfast, and the loyalist workers' strike that destroyed it in 1974.
He believed that Heath's Labour successor, Wilson, could have saved the executive had he been prepared to face down the loyalists, but that Wilson lacked the resolve. Others blamed the defeat of power-sharing on the insistence on an Irish dimension for the executive by FitzGerald and his northern ally, John Hume, then Gerry Fitt's deputy in the SDLP.
Hume had a similar family background to FitzGerald, if less socially elevated. Their philosophical similarities showed in the policies of the SDLP, which shared much with FitzGerald's writings, including his 1972 book, Towards a New Ireland.
The two worked together in Ireland, Europe and the US to move Ireland away from the politics of the 1922-23 civil war, to move Northern Ireland away from its obsession with the border, and to push the British to constitutional change. Their differences were of implementation rather than principle. Sometimes they clashed in claiming the laurels for successes, but they generally worked as a team to milk the 40 million-strong Irish diaspora in the US, and use the Catholics of Europe to promote their policy of creating the economic and social climate for reconciliation.
Successive US governments were persuaded to help press the British into a constitutional settlement and to create cross-border institutions. FitzGerald had close links with Senator Edward Kennedy. With the Kennedy clan, he worked to harness Irish-American sympathy and investment for constitutional politicians rather than for the IRA. The 1985 treaty, into which the British were railroaded after a 1984 visit to Ireland by President Ronald Reagan – and in which Britain conceded that it no longer had a strategic interest in staying in Northern Ireland – sprang out of his alliance with Hume and with Irish America.
FitzGerald also used Europe to add to the pressure on Britain. Jack Lynch's Fianna Fáil government began the process of taking Britain to the European Commission on Human Rights to achieve a ruling that interrogation methods used during internment in 1971 were inhuman and degrading. As foreign minister to the Fine Gael taoiseach Liam Cosgrave, FitzGerald continued the process, and in 1977 the UK attorney general told the European Court of Human Rights that the methods would not be reintroduced.
During his first term as taoiseach, the deaths of Bobby Sands and nine other IRA hunger strikers in the Maze prison, near Belfast, in 1981 left him temporarily without influence in Northern Ireland. FitzGerald then worked with Hume and the Norwegian Torkel Opsahl to bring the debate over the lack of democracy in Northern Ireland on to the European parliamentary agenda.
When he became taoiseach, Anglo-Irish relations were in the doldrums. FitzGerald concocted the New Ireland Forum as a talking shop to seek solutions. He found his party, with Ireland in recession, hard to persuade. He and his foreign minister, Peter Barry, were outvoted 10-2. FitzGerald held individual talks with each cabinet member, winning them over by pointing out that if they did not agree, Haughey, whom Hume was wooing, would come out with his own proposals.
FitzGerald's relationship with Haughey, whom he heartily disliked and distrusted, dated back to their days as students at University College, where they were briefly both in pursuit of the same young law student, Joan O'Farrell. In later years she always said of Haughey, "I liked him." But it was the dashing FitzGerald, the brighter, more urbane mind, who attracted her.
Their marriage, which lasted from 1947 until her death in 1999 after almost 30 years of pain from arthritis, was a partnership at all levels. Even as taoiseach, he had an alarm set at 3pm and went home to help with her medication. Reputedly, on only one decision, a childcare issue, did he fail to consult her, and it was a disaster.
After Fine Gael's election defeat in 1987, FitzGerald left frontbench politics, and in 1992 the Dáil. He went back to writing, as a regular contributor to British, Irish and American newspapers. He also returned to the business world, as a director of the International Institute for Economic Development and of Guinness Peat Aviation.
Following Joan's death, FitzGerald, increased his journalistic output, writing primarily about global economic links, and using his position with the International Institute to travel widely, keen to promote the economic wellbeing of the new Ireland he had helped to gestate. A continuing supporter of the European Union, in 2002 he returned to political campaigning in favour of the Nice treaty, and in 2009 for the Lisbon treaty. He is survived by two sons and a daughter.
• Garret FitzGerald, politician, born 9 February 1926; died 19 May 2011
