[1][a] Gerard served in the King's army as an ensign, and by the early 1650s had entered the shady world of Royalist conspiracies to overthrow the Commonwealth and restore Charles II to the throne.
The night before the murder Gerard had overheard Pantaleone Sá and his friends talking of English affairs in the street and had given them the lie, whereupon they had attacked him, and, though a little man, yet "he threw him off that was upon him, and so was hustling with him a good while", but was rescued by a passer-by, after he had received a stab in the shoulder.
[3] Don Pantaleon Sá was affronted by what he perceived to be a slight on his honour and he returned to the location the next day with an armed retinue to seek revenge.
It was alleged that in company with a Royalist major, one Henshaw, whom he had met in France, Gerard with 30 other mounted men were to attack the Lord Protector, Oliver Cromwell as he rode to Hampton Court, and, after overwhelming his body guard and killing him, to besiege Whitehall,[5] seize the Tower of London, and proclaim Charles II king.
He turned to the crowd and told them he was not permitted to speak, and intimated his words would be published, and then continued with vehemence: I die a faithful subject and servant to King Charles the second, whom I pray God to bless and restore to his rights; and had I ten thousand thousand lives I would gladly lay them all down thus for his serviceThe Royalist writers published a copy of his prepared speech, and affirmed that he fell into a trap set by Cromwell.