The Irish Republican Brotherhood exploded a bomb at Coldbath Fields Prison (Clerkenwell Gaol) in London. Several passers-by were killed. Several of the perpetrators were arrested and hung in 1868.
Editors. "Fenian brotherhood Clerkenwell bombing". The Literary Encyclopedia. First published 01 February 2010
[http://www.litencyc.com/php/stopics.php?rec=true&UID=7219, accessed 21 August 2014.]