I was responsible for a secure radio-relay link between Stormont Castle and Lisburn, which then connected in to the Divis Mountain-Stranraer-London link. That was in 1973. I was driven to SC, dressed in civvies, usually in a Moggie 1000 Traveller.I should state that it was defined as smart civvies, ie jacket and tie, with the L9 in a shoulder holster. Other jobs, which required our technical expertise, but somewhat covert, like the voice-disguising device for witnesses at the Commissioners Court, were also carried out in civilian dress. We loved the court job - ever heard a Dalek with a broad Irish accent ? HILARIOUS !!