Well he's obviously not in a hurry for it, so just put it somewhere safe and give it to him next time he decides to show up. Do you have his new address? The other option would be to write his new address on the envelope, mark it "Forward to" and stick it back in the postbox.
You can't honestly expect plain English from a government office now, can you
Both 50 S14 M 16 yrs (his 3rd; my 1st)
ILYBINILWY - 24 Dec 2012 H moved out - 27 Jun 2013 Legally separated - 6 Sep 2013 Closing the door and changing the locks