From February to May 1922, The Shelbourne played host to its most historic meetings: the drafting of Ireland’s first Constitution. Under the chairmanship of Michael Collins, the committee met in room 112, to write the Constitution of the Irish Free State. This room is now The Constitution Suite, and contains the original table and chairs.
https://www.theshelbourne.com/history
In February 1922, when the Irish Free State was about a month old, the provisional government held a special meeting to set the Constitution.
“The team: Mr. Michael Collins, Chairman; Mr. Darrell Figgis, Acting Chairman: Mr Hugh Kennedy, Mr. James Murnaghan, Mr James MacNeill, Professor Alfred O’Rahilly, Mr. Kevin O’Neill, Mr. John Byrne. Assistance is being given by persons who are acting in specialized capacities.”
Munster News 01 February 1922
The Constitution took about six months to complete was ratified by the Dail in October 1922. Darrell Figgis, vice-chairman, did the lions share of work on it as chief, Michael Collins was frequently absent from the committee, due to his other political commitments. Having spent so much time working on it, later that year he published a book entitled; The Irish constitution explained.
Sources
https://www.theshelbourne.com/history
Munster News 01 February 1922