https://en.wikipedia.org/wiki/Marsha...oyal_Air_Force
Marshal of the Royal Air Force (MRAF) is the highest rank in the Royal Air Force (RAF).[1] In peacetime it was granted to RAF officers in the appointment of Chief of the Defence Staff (CDS), and to retired Chiefs of the Air Staff (CAS), who were promoted to it on their last day of service. While surviving Marshals of the RAF retain the rank for life,[2] the highest rank to which officers on active service are promoted is now air chief marshal. Although general promotions to Marshal of the Royal Air Force have been discontinued since the British defence cuts of the 1990s, further promotions to the rank may still be made in wartime, for members of the Royal Family and certain very senior RAF air officers in peacetime at the discretion of the monarch; all such promotions in peacetime are only honorary, however.
The option still exists, it would seem.