From Wikipedia:

“The medal has been historically used to recognise the service of police officers who work in protective services, gardeners, housekeepers, drivers, valets and other similar type staff. Non-commissioned members of the military may also be awarded the medal for services. The medal is often awarded for service to the monarch and royal family during royal visits. The medal may be looked upon as a long service medal, but the service must be of a meritorious character to warrant its award.[5]”

“Originally ranked near the end,[7] the medal now ranks ahead of campaign, jubilee, efficiency, and long service medals in the United Kingdom Order of Wear.[8] This gradual increase in importance was marked by the July 1980 approval, by Queen Elizabeth II, to allow the use of the postnominal RVM by recipients of the medal.”