In January 1751 during a by-election to Parliament, Murray supported the opposition Whig candidate Sir George Vandeput, 2nd Baronet.

Upon release he was driven to his brother's house in Henrietta Street near Covent Garden, being cheered by a numerous crowd carrying a banner with the words "Murray and Liberty" inscribed.

The plan was to kidnap King George II and other members of the Royal Family on 10 November 1752 and place them on a boat in the Thames that would sail to France.

Detailed analysis of the sentry system at St James's Palace was taken down and two or three hundred men were chosen to congregate at Westminster, though to avoid suspicion they would lodge at separate properties.

On the night that the King would be abducted, they would assemble at pre-planned locations, with St James's being seized, the Tower of London's gates opened, the guards overwhelmed and the Royal Family smuggled to France.