Only it's not just us any longer; it's every country leaving every other country. The border posts are being manned. The planes have stopped flying.
Major cities are going into lockdown (so who'd want to travel, anyway?)
People are being told to stay at home. The police are telling them. The uniforms are in charge.
Britain is a little behind the rest of the continent in imposing restrictions and closing things down; It was always thus...
I'm reading Kate Atkinson's Transcription- which (in its early stages anyway) is set during the phoney war of 39-40, before the bombing and the Battle of Britain. Hitler is collecting countries as if they were stamps, France will be falling soon- and our pov character finds herself- without ever having applied for the job- spying on home grown Nazi sympathisers, all of them more pathetic than sinister. She doesn't quite know what she's doing or why- and has little idea of what her superiors are up to- or which of them she should trust. I imagine the atmosphere of then is rather like the atmosphere of now.