wall of silence/secrecy
From Longman Dictionary of Contemporary Englishwall of silence/secrecywall of silence/secrecySAYa situation in which nobody will tell you what you want to know The police investigation was met with a wall of silence. → wallExamples from the Corpuswall of silence/secrecy• A wall of silence has now descended over the key players.• Blount met with a convenient wall of silence.• Very soon a cold stone wall of silence had tormented them to wounded exasperation.• But the wall of silence that protected behind the scenes negotiations produced no answers.• Other cracks in the wall of secrecy have appeared in recent years, as we shall see in Chapter 5.