In February 1948, a Fine Gael-led coalition ousted Eamon de Valera from 16 years of rule. That summer, the British Prime Minister, Clement Attlee, was assured that Anglo-Irish relations were friendlier than ever. Nine months later, the Taoiseach, John Aloysius Costello, was threatening to hit the British government "in their prestige, and in their pride and in their pocket".

The intervening period saw Eire's surprise withdrawal from the Commonwealth and the birth of the Republic on Easter Monday, 1949.

The Irish Free State had been a member of the Commonwealth since signing the 1921 Treaty. This meant that a Governor General, acting on behalf of the King, summoned and dissolved the Dail, signed acts of the Oireachtas, appointed judges and members of the Executive Council.

The Governor General kept a judiciously low profile and rarely questioned legislation. However, when in 1926 Vice-President of the Executive Council Kevin O'Higgins considered abolishing the right of appeal to the Privy Council, he was informed by the Dominions Office that the Governor General would be instructed to reserve the Royal Assent.

Four years later, the Dominions Office agreed, provided "the Protestant minority were content and did not oppose". This was in accord with the stepping-stone gradualist approach to independence favoured by Cumann na nGaedheal.

Then, in 1931, the statute of Westminster gave Commonwealth members the legal right to revoke treaties and to withdraw from the Commonwealth.

According to Costello, Eamon de Valera, when elected to power in 1932, took advantage of this and proceeded to accomplish almost all the things which Fine Gael and its predecessors had tried to do by friendly negotiation. He removed the oath of allegiance to the crown that Dail deputies swore, abolished the appeal to the Privy Council and downgraded the office of Governor General by nominating a greengrocer to the office, before finally abolishing it in 1937. Costello was irritated that the British government had not the foresight to allow the Cosgrave government to modify the treaty and blamed them for Fianna Fail's electoral success in 1932.

The link with the Commonwealth was further diluted following the sudden abdication of King Edward VIII in December 1936. De Valera decided to recognise the abdication and deleted all mention of the king and the Governor General from the 1922 constitution. Simultaneously, he decided to reappoint the king's successor by making him titular head of the State's external relations. This was popularly called the External Relations Act. It was accepted by Britain as a sufficient link to retain membership of the Commonwealth.

In practice, the External Relations Act allowed the British monarch to continue to appoint and receive envoys and ratify treaties on the State's behalf. De Valera had decided to remain in the Commonwealth in order to provide an umbrella under which Northern Ireland could come "into association with Eire".

After the second World War, there was an international climate in favour of independence and decolonisation. Eire had proved it could defend its sovereignty. On the world stage, it was embarrassing for Eire that exchanges of envoys were accredited through the British monarch. At home, this went unnoticed until the summer of 1947, when the Irish Ambassador to the Vatican, Joseph Walshe, was kept waiting in Rome for three weeks to have his credentials signed by the king.

This highlighted the fiasco whereby the Ambassador from Eire to the Vatican had his letter of credence written in Irish addressed to the Pope, but signed by King George VI. In this instance, the king diplomatically deleted the title "defender of the faith", bestowed by the Vatican upon a once-faithful Henry VIII.

De Valera was not amused by the delay. In October, he complained to Lord Rugby, the British Minister in Eire, that the External Relations Act had involved him in "constant criticism and humiliation" and had not acted as the intended bridge which would help to solve Anglo-Irish difficulties. He instructed his Attorney General, Cearbhall O Dalaigh, to draft a Bill to repeal the Act.

His first draft did not mention the term Republic, but by January 1948, on the eve of the general elections, he redrafted the Bill and included a reference to the State as a Republic.

Fianna Fail did not include repeal of the External Relations Act in the manifesto for the general election of February 1948. Neither did Fine Gael, which stood for retaining the link with the Commonwealth.

Garret FitzGerald in his autobiography remembers his wife and himself "reassuring the inhabitants of Waterloo Road on the point". The new republican party Clann na Poblachta, led by Sean MacBride, was the only party to propose repealing the link with the Commonwealth. A Fine Gael-led coalition, supported by Clann na Poblachta, was elected in February 1948. MacBride was appointed Minister for External Affairs and agreed to place his policy of repeal "in abeyance".

REPUBLICAN supporters in his party, including former members of the IRA, pressurised him to get some tangible movement on partition. In the summer of 1948, MacBride asked General Peron of Argentina, who was in dispute with Britain over the sovereignty of the Falklands/ Malvinas, to bypass the procedures of the External Relations Act and appoint his minister directly to President Sean T. O'Kelly instead of King George VI.

At the beginning of September 1948, Costello made a speech to the Canadian Bar Association in Montreal about the "inaccuracies and infirmities" of the link with the Commonwealth. The speech implied that the External Relations Act was archaic and defunct. Costello hoped the procedures relating to the External Relations Act would be allowed to quietly wither away as had happened in the appointment of the minister from Argentina and that Eire could still retain a new type of "associate" membership of the Commonwealth.

As part of this plan to recognise Eire as a separate state outside the Commonwealth, Costello, while dining in the Governor General's residence, had arranged to have a toast to the President of Ireland offered in return to the toast to the king. If the toast had been honoured it would have been recognition by Canada, a leading member of the Commonwealth, that Eire had a separate head of state, namely its own president, who would represent it in international affairs.

This toast to the President was reneged upon by the Governor General, Lord Alexander (an Ulsterman and former 1914 mutineer).

Costello noted that and other snubs, in particular having a replica of the cannon "Roaring Meg" placed on his table. This was used in the 1689 siege of Derry against the army of the Catholic King James II. Costello was upset but reserved his comments for a later meeting with the Canadian Prime Minister, Mackenzie-King.

While Costello was in Canada, MacBride issued a press release quoting selective parts of Costello's speech. A banner headline, "External Relations Act to go", appeared in the Sunday Independent on September 5th.

MacBride telephoned Costello in Ottawa to discuss a response to the Sunday Independent's speculation. No decision was arrived at. Two days later, on September 7th, a press conference was held in the Railway Committee room of the Ottawa Parliament Buildings. He was asked by the assembled world press if it was Eire's intention to repeal the External Relations Act.

He confirmed the speculation, mentioning the possibility of continuing as an associate member of the Commonwealth. His reply became known as "the announcement".

While the British government was surprised, it was not to know that so too was the Irish Cabinet, including MacBride.

Costello was surprised by the reaction of the press. It was, after all, an admission of an intention only and not a cabinet decision. On the day after the announcement, MacBride, apparently without consulting Costello, or any departmental secretaries, drafted a Bill to repeal the External Relations Act. The Assistant Secretary in the Taoiseach's Office challenged MacBride's authority and returned the draft Bill to him. MacBride then instructed the Assistant Secretary to proceed with the Bill.

Three days after Costello's announcement, the British cabinet, annoyed at not being consulted in advance, decided to withdraw an invitation to Eire to attend the October meeting of Commonwealth Ministers in London. This was tantamount to terminating Eire's ambiguous membership of the Commonwealth.

During that month of September 1948, the British government was in the midst of the Berlin crisis and feared a European nuclear war with Russia.

It was concluding talks in Washington regarding NATO membership and its charter. Britain had lost its empire but still hoped to lead Europe, buttressed by a united Commonwealth owing allegiance to the crown.

Britain was especially worried that India, which was about to become a republic, might be influenced by Eire's example, leave the main body of the Commonwealth and end up in the Russian camp. This would have a domino effect and make Australia and New Zealand look to south-east Asia for a defence pact.

GIVEN the international tension during that year, Costello's surprise announcement was considered to be yet another opportunistic stab against Britain.

In October 1948, the British government considered appealing over the heads of the Irish government to the people, emphasising the possible repatriation of Irish aliens, hoping it "would cause panic about the possible uprooting and displacement of Irish citizens that would make the Irish government think twice about their course of action".

Shortly after returning to Ireland, Costello rallied support. According to Dr Noel Browne, Minister for Health in that government, Costello called a "caucus meeting of the Cabinet" at his home and "visibly distressed" offered his resignation. This strategy was rejected by his government. Instead, as Irish cabinet papers show, they approved, retroactively, "the action" Costello took in Canada.

Tortuous diplomatic negotiations ensued. With the support of the Prime Minster of New Zealand, Peter Fraser, and, in particular, the Deputy Prime Minster of Australia, Dr Herbert Evatt, Eire, although outside the Commonwealth, re tained most-favoured nation status in relation to trade and citizenship benefits.

The Republic of Ireland Bill which repealed the External Relations Act and described the status of the State as a Republic was published in the Dail on November 17th, 1948. Notably, as though indicative of an overall lack of consultation and planning, the Cabinet had decided only five days before to include the term republic. The Act was signed by President Sean T. O'Kelly on December 21st, 1948, but delayed until Easter Monday 1949, when the Republic of Ireland Act was formally inaugurated.

Fifty years later the constitution has still not been amended to acknowledge that status.

Ian McCabe is the author of A Diplomatic History of Ireland 1948- 49: The Republic, the Commonwealth and NATO (Irish Academic Press).

Tomorrow: John Coakley of UCD assesses the enduring relevance of events in 1949.