Two Saturdays in succession, King William III did not ride out to hunt. For Robert Charnock and the horsemen who lay in wait for him near Brentford, this change of royal purpose brought the assassination plot to nothing before a single blow could be struck. At trial, the central inquiry concerned not a consummate murder, but clandestine assemblies, rosters of cavalry, and the depositions of men who had already confessed their own guilt.
Charnock, Edward King, and Thomas Keys were brought to the bar of the Old Bailey on 11 March 1696 to answer an indictment of high treason. The Crown charged them with a design aimed at compassing the King's death and overthrowing his realm. Some forty horsemen were to lie in ambush along a narrow lane between Brentford and Turnham Green, fall upon the royal coach upon its return from the chase, and cut down the guards. According to the witnesses for the Crown, this slaughter was to serve as the prelude to a French descent upon the coast, intended to restore James II to his throne.
The accusation reached back to the preceding year. Secret meetings had allegedly taken place, but the King departed for Flanders, and the conspirators had secured no vessel to cover their flight following the deed. The scheme revived upon the arrival of Sir George Barclay and several officers from France. The conspirators convened in London taverns and private lodgings, debating the merits of various grounds for an ambuscade: Richmond, Kew, and finally the highway between Brentford and Turnham Green.
The design unfolded before the bench distributed the several parts. Barclay was to lead an assault party against the coach itself. Charnock and Captain Porter were to direct the onslaught against the horse guards; yet another detachment was to wheel upon the flanks. Some forty mounts were to be mustered, the men quartered by small squads in outlying inns, while two lookouts stationed at Kensington were to warn the commanders the moment William set forth. Crown testimony further maintained that the plotters had reconnoitred the ground with deliberate care.
The fifteenth of February was first chosen for the deed. The men made ready, but word arrived that the King would not ride out. The rendezvous was dismissed. A week later, the apparatus was set in motion anew: the men assembled, the rolls were inspected, and a carbine capable of discharging multiple musket balls was entrusted to one of the confederates. At noon, a second countermand arrived: the King would not go abroad that day either. The guards turned about, the coaches were returned to the royal mews, and the conspirators scattered, some immediately seeking secret harborage.
Porter stood as the foremost witness for the prosecution. Admitting his own share in the treason, he detailed the rendezvous, the conversations, and the assigned roles. Charnock, he swore, had urged him to procure men for the enterprise. The confederates, he maintained, sought the restoration of James II, persuaded that a French invasion would follow hard upon William's death. Porter had an urgent reason of his own to speak: having confessed his participation, he could hope to preserve his neck only by testifying against his fellows.
Charnock pressed this point in his defence. Porter was not merely an accomplice turned King's evidence, but a man whose very life hung upon the edifice of accusation he was now constructing. The other depositions displayed similar infirmities. De la Rue recounted conversations and intentions; Pendergrass corroborated the meetings and projects, though admitting that certain designs had never been fully revealed to him. Bentham claimed that Charnock had spoken of "taking off the King," an expression the prisoner vigorously denied. The bench left the credibility of these accomplices to the jury's conscience, while ruling their testimony strictly admissible under the law.
Charnock did not deny having ridden across the countryside with other gentlemen, nor having taken part in political discussions. He contested, however, any evidence that he had entered into a specific design of assassination. He swore he had never seen any royal commission from James II, arguing that the Crown witnesses substituted their bare words for the absence of overt acts. The ride upon the road might well have been an ordinary excursion; the phrase "taking off the King" was capable of innocent construction; and the narratives regarding who attended which assembly abounded in contradictions.
Edward King maintained that he had ridden into the country with Porter and Knightley merely to take the air. He denied that De la Rue had ever spoken to him of an assassination, pointing out that the witnesses were often unable to state precisely what "design" was being canvassed. Thomas Keys pleaded that he was merely Porter's domestic servant and had done no more than obey his master's commands. The judge answered that servitude to a master was no warrant for treason if the jury found that Keys had knowledge of the plot. The deposition books showed that he had purchased horses and attended several of the gatherings.
The question of the law's due process ran through the entire defence. The prisoners were denied a copy of their indictment and the assistance of legal counsel; the court ruled that the statute extending those privileges to persons accused of high treason had not yet come into operation. Charnock pressed the recent enactment of that reform and urged the natural equity of its principles. The court held fast to its refusal. The defendants likewise challenged the legal weight of evidence tendered by former accomplices, but the judge reiterated that the common law received such testimony, leaving its credit to the evaluation of the jurors.
In summing up to the jury, the judge drew a sharp distinction between idle discourse and a true overt act. Words unattached to an enterprise could not suffice, he instructed; but to solicit a man to an assault, to provide the instruments, or to prepare an ambuscade were overt acts that unmistakably manifested a treasonable intent. He laid down the rule and applied it directly to the tavern meetings, the marshaling of the horsemen, and the reconnaissance of the road.
All three men were found guilty. They were executed at Tyburn on 18 March 1695/96. In the written paper left before his death, Charnock admitted his share in the planned attack upon the Prince of Orange and his guards, but denied having known of any commission from King James authorizing the murder. Edward King likewise declared that he had never seen nor known of any royal order, acknowledging that he had been undone by his own rashness. These dying confessions did not challenge the justice of the sentence; rather, they drew a line between the isolated action of a small band of men and a royal command or general Catholic rising, which both prisoners firmly denied.
Along the narrow way where they had planned to wait in ambush, no royal coach had ever been stopped. Yet the muster rolls and the depositions of former confederates were enough to convey the three men to Tyburn. Keys, the servant who pleaded that he had merely obeyed his master, perished beside the two gentlemen; Porter, the master turned Crown witness, had chosen another road to save his own life.