[arch-general] Where's my locale gone?

[Paul Gideon Dann]

I'm stumped: I've had LANG=en_GB.UTF8 in /etc/locale.conf ever since the
switch to systemd, but in the last few days since my previous reboot,
something's changed (maybe systemd 216?) and now I find that, even though
/etc/locale.conf still contains en_GB, I get:

# echo $LANG
en_US.UTF8

This is almost certainly related to why I'm getting messed up character
encoding in Konsole. In particular, tmux fails to render dividing lines
properly, showing accented 'a' characters instead, and similar things
happen in Vim.

Is there some additional configuration I need beyond /etc/locale.conf now?
I've checked locale.gen and rerun locale-gen without any effect. I've also
tried rerunning mkinitpio for good measure.

Any ideas?

Paul