During the Treaty negotiations, the British were prepared to allow Ireland to withdraw from the UK, but they insisted the country remain within the British Commonwealth. In theory the dominions of the Commonwealth were subservient to the British king, but countries like Canada and the Union of South Africa claimed that they were really independent, because the British Crown was only symbolic.

“The British Dominions have been conceded to them all the rights that Irish Republicans demand,” President Éamon de Valera declared in written response to questions from the Manchester Guardian in Feb 1921. “It is obvious that if these rights were not being denied to us we would not be engaged in the present struggle.”

Although de Valera recognised that Canada was independent despite her ties to the British Commonwealth, he contended that Ireland needed to be outside the Commonwealth to be ensured of the same status as Canada.

The British countered this by offering to specify in the proposed Treaty that the Irish Free State would have the same status as Canada in “law, practice, and constitutional usage”.

The British insisted, however, that members of the Irish parliament should take an oath to observe the terms of the Treaty.

Michael Collins proposed an oath on Nov 30, 1921, that would primarily be to the Irish Constitution: “I… do solemnly swear to bear true faith and allegiance to the Constitution of the Irish Free State as by law established and that I will be faithful to His Majesty King George in acknowledgment of the Association of Ireland in a common citizenship with Great Britain and the group of nations known as the British Commonwealth.”

The British did not accept this. The next day, they gave the Irish delegation draft proposals for consideration. These contained an oath in accordance with which members of the Dáil would swear “true faith and allegiance to the Constitution of the Irish Free State… and to the King as Head of the State and of the Empire”.

When the Irish delegation met with the Cabinet in Dublin on the afternoon of Saturday, Dec 3, Collins said he would not accept the oath as drafted. He believed they could get a more acceptable form.

On his arriving back in Dublin that morning, he had sent a copy of the draft Treaty to the IRB colleagues for their consideration. During a lunch break, he had a hurried meeting with the IRB secretary, Seán Ó Muirthile, who explained that their colleagues had reservations about the oath.

He gave Collins an alternative oath that was comparatively similar to the one that Collins had already suggested to the British.

“The oath crystallised in itself the main things we objected to,” de Valera later wrote. “It is obvious that you cannot have that or anything like ‘to the King as head of the State and the Empire’,” he explained. “You could take an oath of true faith and allegiance to the Constitution of Ireland.” de Valera suggested: “I… do swear true faith and allegiance to the constitution of the Irish Free State, to the Treaty of Association and to recognise the King of Great Britain as Head of the Associated States.”

The next day in London, a dispute erupted within the Irish delegation over whether de Valera had suggested they recognise the British King “as Head of the Associated States”, as the acting cabinet secretary Colm O Murchada had recorded in the minutes.

This could be interpreted as recognising the king as head of each state individually as well as the head of the combined association of states. Collins and Arthur Griffith agreed with O Murchada, but Robert Barton and Erskine Childers contended that de Valera had only proposed recognising the king as “Head of the Association”.

Barton produced his notes, which proved inconclusive because he had written ‘Head of the Assoc’. Childers recorded in his diary that the president had suggested “King of the Associated States”.

When de Valera later contended in the Dáil that he had said “Association”, he found himself confronting formidable evidence, and he undermined his own argument when he explained that he had advocated: “I do swear to recognise the King of Great Britain as Head of the Associated States.”

“That is the way I expressed it verbally, meaning the association of states.” In other words, he said “Associated States” but meant “Association”.

The British rejected the alternative Irish document the following day and negotiations broke down briefly until Collins was persuaded to meet privately with prime minister Lloyd George. Collins explained that the oath was causing a real problem, and he handed George the form he had proposed the previous week.

The British accepted this with minor modifications. The oath read: “I… do solemnly swear true faith and allegiance to the Constitution of the Irish Free State as by law established, and that I will be faithful to H.M. King George V, his heirs and successors by law, in virtue of the common citizenship of Ireland and Great Britain and her adherence to and membership of the group of nations forming the British Commonwealth of Nations.”

The only real difference from the initial form Collins suggested was the inclusion of a king’s “heirs and successors by law”. Thus, it was Collins who essentially proposed the controversial oath, but who had advised him on it is another matter.

“Mr Collins himself told me that the oath was drafted by Lord Birkenhead,” de Valera later said. Collins got on well with Birkenhead and the story seems plausible.

“Collins further told me,” de Valera added, “that when the draft was completed, Lord Birkenhead passed it over admiringly to him, with the remark: ‘The greatest piece of prevarication in history’.”

* Ryle Dwyer is author of I Signed My Death Warrant: Michael Collins & the Treaty, published by Mercier Press in paperback.