In 1867, the IRB was preparing to launch an armed uprising against British rule in Ireland, but their plans became known to the Dublin Castle administration, and members of the movement's leadership were arrested and convicted.

In the previous weeks, a series of meetings of thousands of people regarding the three men convicted of Brett's murder had been held nearby on Clerkenwell Green, with a deputation sent to the Home Office and petition to Queen Victoria seeking clemency.

Further enquiries into his claim to have been in Glasgow at the time of the bombing were unable to disturb the sentence, and Barrett was hanged by William Calcraft on the morning of Tuesday 26 May 1868 outside Newgate Prison.

Burke protested that he was not a subject of the Queen, but a soldier of the United States, but evidence was provided that his mother and sister lived in Ireland, and he was convicted nonetheless.

The radical, Charles Bradlaugh, condemned the incident in his newspaper the National Reformer as an act "calculated to destroy all sympathy, and to evoke the opposition of all classes".

[citation needed] The day before the explosion, the Prime Minister Benjamin Disraeli, had banned all political demonstrations in London in an attempt to put a stop to the weekly meetings and marches that were being held in support of the Fenians, with a similar vice-regal declaration in Ireland.

The Metropolitan Police formed a Special Irish Branch at Scotland Yard in March 1883, initially as a small section of the Criminal Investigation Department, to monitor Fenian activity.

Queen Victoria, reportedly irritated that only one man was convicted for the bombing, wrote to Home Secretary Gathorne Hardy observing that she was "beginning to wish" that perpetrators of such crimes "be lynch-lawed on the spot".

[3] Liberal leader William Ewart Gladstone, then in opposition, announced his concern about Irish grievances within days of the explosion, and said that it was the duty of the British people to remove them.

When Gladstone discovered at Hawarden later that year that Queen Victoria had invited him to form a government he famously stated, "my mission is to pacify Ireland".

[citation needed] In April 1867, the supreme council of the Irish Republican Brotherhood condemned the Clerkenwell Outrage as a "dreadful and deplorable event",[4] but the organisation returned to bombings in Britain in 1881 to 1885, with the Fenian dynamite campaign.

"[7] Parnell also attributed the explosion and the Manchester Martyrs incident as leading to "some measure of protection being given to the Irish tenant" and the Church of Ireland being "disestablished and disendowed".