If the King be abſent, and taken captive, the People may give the Royall power to one, or to ſome few to exerciſe it as cuſtodes regni.
1683, John Nalson, An Impartial Collection of the Great Affairs of State: From the Beginning of the Scotch Rebellion in the Year MDCXXXIX to the Murther of King Charles I, volume II, Thursday the 29th of July in 1641: “Votes to deſire a Vice-Roy during the King’s abſence in Scotland”, page 412
After the Conference with the Lords about the Disbanding, the Commons fell into Debate concerning the Kings Journey into Scotland, and it was, Reſolved, &c. That the Lords be deſired by this Houſe in a Conference, to joyn with this Houſe in a Petition to His Majeſty, to appoint a Cuſtos Regni, or Locum tenens during his Abſence out of this Kingdom; and amongſt other things, in ſpecial to give him Power, to give the Royal Aſſent in Parliament, and to do ſuch things as the King might do if he were preſent. Reſolved, &c. That His Majeſty be likewiſe Petitioned, That an Act of Parliament may paſs to this Effect, That ſuch Commiſſion ſhall not be repealed, until His Majesties return from Scotland to the City of London or Weſtminſter, or be preſent in full Parliament. Which two Reſolves were communicated to the Lords at a Conference.
From this time it seems to have been most usual to appoint custodes regni, or locum tenentes, the first instance of such appointment being in the thirty-seventh year of Henry III, when the Queen and the Earl of Cornwall were made guardians of the realm during the King’s absence in Gascony.
