Athough SUID is set for the enable command, it still disallowed users other than root or lp to use it.
I've now added my username to /etc/auth/subsystems/lp
adm
rintqueue,printerstat
audit
rintqueue,printerstat
auth
rintqueue,printerstat
bin
rintqueue,printerstat
daemon
rintqueue,printerstat
lp:lp
sys
rintqueue,printerstat
root:lp,printqueue,printerstat
david:lp,printqueue,printerstat
It still doesn't let me use the command, so maybe I need to restart to pick up the new authorisation.