Honourable Artillery Company

The Honourable Artillery Company was incorporated by Royal Charter in 1537 by King Henry VIII and is the second oldest military organisation in the world (behind the Vatican’s Pontifical Swiss Guard). Today it is a Registered Charity whose purpose is to attend to the "better defence of the realm". This purpose is primarily achieved by the support of the HAC Regiment and a detachment of Special Constabulary to the City of London Police.

More information on the Wikipedia page