Yes indeed Eddie, too little too late although there was a belated recognition in the end. I witnessed some of the residual nervousness in people who began to speak out about wartime events in the mid seventies, so that's one "Official Secrets" explanation. Other's have suggested that there might have been a class element ie Mr Flowers was "only" a GPO engineer. There could be some documentation not yet yet revealed but Churchill appears to have been very concerned to "clear the decks" as we entered the Soviet Era, so our technology did not fall into the hands of others. We seem to be back in that sort of a situation again, here in 2020
Dave W.