The Cato Street Conspiracy was as follows: Some of the desperadoes were to watch No. 39 at a convenient distance, while one of the group was to call at the house and deliver a dispatch box. Then, when the door was opened, the others would rush in and murder the Ministers as they sat at dinner.
Their most brutal act would be to bring away the heads of Lord Sidmouth and Lord Castlereagh, at whom the conspiracy was primarily directed, as trophies of their success, in two bags provided for the purpose.
Further depredations were predicted with the help of the people who, they calculated, would rise as in revolutionary Paris, at the sight of the mangled remains of their oppressors!
Greville stated that the conspirators intended to fire a rocket from Lord Harrowby's house as soon as their dastardly deed was accomplished, as a signal to their friends. An oil shop was then to have been set on fire to add to the confusion and to attract a mob, and then the Bank was to be attacked and Newgate thrown open.
The plot was revealed by Edwards, who had wormed himself into the confidence of Thistlewood and his confederates, and information was given to those concerned. However, it was decided that no others should be made aware of the fact, and the preparations for the dinner went on as if nothing was anticipated.
This wise resolution also seems to have suggested itself to Lord Lyndhurst, then Solicitor General, who thought it the best means of accomplishing the capture of the conspirators.
Lord Eldon apparently exclaimed on hearing this advice, "You won't be there! I strongly object to the dinner taking place." However, he was overruled.