Wikipedia: Riot Act:
If any persons to the number of 12 or more unlawfully, riotously, and tumultuously assemble together to the disturbance of the public peace, and being required by any justice by proclamation in the King's name in the exact form of the Riot Act, I George I, Sess. 2 c. 5 s. 2, to disperse themselves and peacefully depart, shall to the number of 12 or more unlawfully, riotously, and tumultuously remain or continue together for an hour after such proclamation, shall be guilty of a felony.
**The Form of Proclamation is as follows:—
Our Sovereign Lord the King chargeth and commandeth all persons, being assembled, immediately to disperse themselves, and peaceably to depart to their habitations, or to their lawful business, upon the pains contained in the Act made in the first year of King George the First for preventing tumults and riotous assemblies.
GOD SAVE THE KING.