In times gone by RNR (Wavy navy) RMR and the Crabs and Pongo equivalent, were considered to be civvies playing at service men personnel, or civvies that did not make the grade for service men personnel But that is definitely not the case these days, they now end up at the sharp end where any active service personnel would be sent.
Yes there will be a lot of BS pomp and ceremony goes with the duty, but the RMR civvies took great pride in gaining the not too easy to attain green beret, and where it with pride, so I can easily see why some if not all those selected to guard the castle will class it as an honor, plus Edinburgh is a good run for days off bonus.
Luckily i never had to do any ceremonials when i was a regular but a few of my muckers did. They stated that all the march and starch aside, they actually felt an immense sense of pride doing it. That, and all the hotel phone numbers they were given by female tourists.