When his practices were detected he made an ample confession, and pleading guilty to his indictment at the Old Bailey, was condemned to death for high-treason.

At the same time, John Bara and Alexander Valiere were committed to Newgate for corresponding with the enemy; and Claude Baud, secretary to the duke of Savoy's minister, was, at the request of his master, apprehended for traitorous practices against her majesty and her government.

A committee of seven lords being appointed to examine these delinquents, made a report to the house, which was communicated to the queen, in an address, importing, that Gregg had discovered secrets of state to the French minister: that Alexander Valiere and John Bara had managed a correspondence with the governors and commissaries of Calais and Boulogn; and, in all probability, discovered to the enemy the stations of the British cruisers, the strength of their convoys, and the times at which the merchant ships proceeded on their voyages; that all the papers in the office of Mr.
Secretary Harley had been for a considerable time exposed to the view of the meanest clerks, and that the perusal of all the letters to and from the French prisoners had been chiefly trusted to Gregg, a person of a very suspicious character, and known to be extremely indigent.

The queen granted a reprieve to this man, in hope of his making some important discovery, but he really knew nothing of consequence to the nation.

He was an indigent Scot, who had been employed as a spy in his own country, and now offered his services to Chamillard, with a view of being rewarded for his treachery; but he was discovered before he had reaped any fruits from his correspondence.