The FAA and AAC always had their service written on the side to make sure nobody made the grave error of thinking they were RAF. It was thought that having a UK roundel and being a military aircraft would be sufficient to identify the RAF in the majority of cases. In these days of branding and corporate logos I guess it's not as obvious to the paying public.
Mind you - they didn't let 800 NAS/Naval Strike Wing put Royal Navy on their GR7/9s.
