1916 WW1 GB PRISONERS OF WAR CONTRARY REGULATIONS + TPO LONDON HOLYHEAD NIGHT DOWN PMKS

LONDON & HOLYHEAD T.P.O NIGHT DOWN postmark dated 3 AP 1916 on envelope; + boxed handstamp in violet CONTRARY TO REGULATIONS Letters for Prisoners of War must be addressed in ink.  

The cover was addressed in pencil, which has since been erased !

Unusual cover.