Bit more info - dmesg - sorry didn't think about it before!
audit: type=1400 audit(1493287998.510:88): apparmor="DENIED" operation="open" profile="thunderbird" name="/mnt/Z/temp/Bluebell/TyreSize.jpg" pid=4537 comm="thunderbird" requested_mask="r" denied_mask="r" fsuid=1900 ouid=1900
audit: type=1400 audit(1493288317.390:149): apparmor="DENIED" operation="exec" profile="thunderbird" name="/usr/lib/firefox-esr/firefox-esr" pid=4906 comm="thunderbird" requested_mask="x" denied_mask="x" fsuid=1900 ouid=0
jimc is uid 1900 paws4pets is gid 1900
