Effects of the explosion at the house of detention, Clerkenwell, seen from within the prison yard: police officers and firemen searching the ruins. The gunpowder explosion on the outer wall of Clerkenwell Prison was an attempt to free two Fenian prisoners, Richard Burke and Joseph Theobald Casey, who were imprisoned there. The explosion destroyed several houses in the neighbourhood, killed several people, including as the Illustrated London News says, "two little children", and injured many more.