What Is The Youngest Age To Be A Monarch?

Question:

What is the youngest age to be a monarch in Great Britain?

Answer:

Neil, Kidderminster.

Any age! However, if the heir is under 18 when the current monarch dies, the 1953 Regency Act states that the next person in line over the age of 18 would be the Regent. This would mean they would act as monarch until the heir turns 18.

Qualification:

History geek!