In answer to the Omega-wearing and Omega occupant-worrying Charlie Golf, it is my understanding that while ROVs (Radio Operators Voice) have flown on board Nimrod R, they did not have an aircrew brevet unless and until they became Air Sig RCs.
My understanding is that an ROV, previously known as a SOV (Special Operator Voice), is/was primarily a ground trade, flown occasionally as required. The 51 Squadron ORBs (now open at Kew) tell us, for example that ROVs (presumably Spanish speaking) augmented the normal crew for Operation Acme, during the Falklands war.
I understand that ROV is an anachronistic term, the trade subsequently being known as CSA(V) (Communication Systems Analyst (Voice)) and most recently as Int An (V) - Intelligence Analyst (Voice).
The situation regarding the brevets historically worn by 51's 'back end' crew seems complex. Initially Special Operators wore an S-for-Signaller brevet, while Supervisors could be AEOs, Navs, Signallers or even, in at least one case Observers. From about 1963, those Spec Ops who successfully completed the Advanced Course at Hullavington became AE Ops, and could wear an AE brevet. Some time after that, passing the Advanced Course became a pre-requisite for both Spec Ops and Supervisors, and all Special Ops became AE Ops or AEOs.
Previously, the squadron's linguists wore no brevet, and at some point (I'd love to know when) they were given the now-vacant Signaller brevet. The number of linguists seems to have increased during the later part of the Comet/Canberra era, to a level approaching that in the Nimrod period.
Reports that the squadron's rear crew eventually received a winged pie brevet cannot be confirmed!