impenetrable

Mr Csoka said the prison's approach had been "incomprehensible" and the defence had faced "impenetrable red tape" in getting a laptop to Mr Doyle.

A warning: The nesting doll of literary references in “Katabasis” will be a delight to some and impenetrable to others.

His downfall, like hundreds of other serious criminals in the UK, had been his trust in the Encrochat encrypted phone network - which was believed to be impenetrable.

After his third consecutive riot, Tovar turned to the Olympic Auditorium, the impenetrable concrete bunker in downtown Los Angeles where he’d hosted Black Flag a year before.

Gurpreet entered the US on 15 January, five days before President Trump took office - believing that he had made it just in time, before the borders became impenetrable and rules became tighter.