Hi Engines
They were dual hatted airframes. They were always on the military register but had 'shadow' BGA Identities (never used).
There is a typo in the earlier post by Random Bloke who I think put T21 but actually meant K21.
Arc
**Ref your Tech Officer role question in your earlier post, in Mk3 and Sedbergh days the Tech Officer would do minor repairs (trained and authorized so to do) but in Glass Fibre days the Tech Officer role was largely limited to paperwork and Tech Liaison with CGMF at Syerston although I did see one change (swap U/S for S) a nosewheel tyre/wheel assembly once !