Robert Emmet's ring, 1790s

The emerald stone in this ring may symbolise imperialism: it came from India and was given by Sir John Temple to his cousin Dr Robert Emmet, the Irish State physician. But the design, cut in Dublin in the 1790s, symbolises something very different: a woman playing a harp, with, in the background, pikes and a liberty cap – emblems of Irish republicanism.

The ring, which seems to have been copied, was used by Emmet’s revolutionary sons, Thomas Addis and Robert, as a seal and apparently as a token of trust.

Myles Byrne, a fellow conspirator in the United Irishmen, recalls meeting Thomas Addis in Paris and giving him “a paper containing the impression of the seal-ring which I had been the bearer of from his brother, Robert. As soon as Mr Emmet had compared this impression with his own seal-ring, he crossed the room, took me in his arms and embraced me with affection.”

Thomas Addis Emmet was among the United Irish leaders interned in Fort George, in Scotland, in 1799 and released in 1802. His younger brother Robert was expelled from Trinity College Dublin in 1798, rightly suspected of radical activities. He went to Paris and discussed with Napoleon (now established as a dictator) and his foreign minister Charles Talleyrand the possibility of a new rebellion, this time focused on the capture of Dublin Castle, the centre of government power.

Robert returned to Dublin in 1802, determined to put this plan into effect. He was in some respects a romantic idealist, but his military ambitions were real. He hoped to link up with a rump of rebels from 1798 who were holding out in the Wicklow hills under Michael Dwyer.

But he also planned to use more sophisticated technology: hinged pikes that could be more easily hidden, short muskets for urban street fighting and signal rockets that he test-fired in the spring of 1803. Emmet and his coconspirators also developed something that would play a significant role in Irish and world history: the improvised explosive device.

These very ambitions, however, contributed to the undermining of Emmet’s strategy when, on July 16th, 1803, an explosion at his rocket depot on Patrick Street blew apart the secrecy of the conspiracy. (In any event, government agents were already well abreast of his plans.)

Emmet panicked. A hastily arranged meeting fixed the date of the rising for July 23rd – before any French help could arrive and before weapons other than pikes could be effectively deployed. Enthusiasm for uprisings in Ulster, Leinster and Munster waned.

On the evening of the 23rd Emmet sent a rocket signal to countermand the rising, which nonetheless unfolded as a confused melee, in which the lord chief justice, Lord Kilwarden, was piked to death.

Emmet and much of the leadership withdrew into the south Dublin hills, but Emmet was arrested in Harold’s Cross on August 25th, taken to the castle, tried on September 19th and executed on Thomas Street the following day.

But Emmet’s youth (he was 25 at the time of his death) and idealism, his dramatic parting from his beloved Sarah Curran, the disappearance of his body and his speech from the dock – “when my country takes her place among the nations of the earth, then, and not till then, let my epitaph be written” – created a myth of heroism and blood sacrifice that lived long after him.

Thanks to Lar Joye

Where to see it National Museum of Ireland – Decorative Arts History, Collins Barracks, Benburb Street, Dublin 7, 01-677 7444, museum.ie