Cool. I hadn't known the exact provenance of that. There's also "thin blue line" meaning police force[0] (separating decent folk from criminals and chaos) as op

Cool. I hadn't known the exact provenance of that. There's also "thin blue line" meaning police force[0] (separating decent folk from criminals and chaos) as opposed to a military force[1] which is a red line. I would add that red lines are topical with Brexit[2] negotiations in the media, lines beyond which this British government is unwilling to step. [0] Movie https://en.wikipedia.org/wiki/The_Thin_Blue_Line_(1988_film) https://en.wikipedia.org/wiki/The_Thin_Blue_Line_(1988_film) and TV show https://en.wikipedia.org/wiki/The_Thin_Blue_Line_(TV_series) https://en.wikipedia.org/wiki/The_Thin_Blue_Line_(TV_series) [1] https://en.wikipedia.org/wiki/The_Thin_Red_Line_(1998_film) https://en.wikipedia.org/wiki/The_Thin_Red_Line_(1998_film) – one of the best films about war ever in my opinion [2] https://www.theguardian.com/commentisfree/2017/dec/05/theresa-may-brexit-red-lines-reckless-hostage-dup-promises-cant-keep https://www.theguardian.com/commentisfree/2017/dec/05/theres...