Which resulted in the following entry in /etc/group

OK, all nice and as it should be. su - bulwynkl then id shows I am a member of group docker.

but.

when I close terminal and restart it

OR

when I log out and log back in again and run terminal,

the group hasn't taken. running id shows no docker group membership. once again - if I run su - bulwynkl, then id, I DO get docker group...

so...

what am I missing - presumably something is holding onto the old session data even for a logout?

N.B. rebooting solved the issue.  but that isn't very satisfactory - fine on a home laptop - annoying, but fine - less so on a production machine...

IIUC, openning a new terminal SHOULD re-read the .bashrc &etc config files...