IIRC he was on extended special leave prior to his retirement date that occurred while he was in Portugal. I suspect that be was not there as part of his police work.
It is not an offence to impersonate a police officer.
http://ukcriminallawblog.com/man-wearing-pig-mask-and-toy-police-officers-helmet-arrested-for-impersonating-an-officer/What’s the offence?
Police Act 1996 s 90 created offences relating to the impersonation of a police officer:
(1) ANY PERSON WHO WITH INTENT TO DECEIVE IMPERSONATES A MEMBER OF A POLICE FORCE OR SPECIAL CONSTABLE, OR MAKES ANY STATEMENT OR DOES ANY ACT CALCULATED FALSELY TO SUGGEST THAT HE IS SUCH A MEMBER OR CONSTABLE, SHALL BE GUILTY OF AN OFFENCE AND LIABLE ON SUMMARY CONVICTION TO IMPRISONMENT FOR A TERM NOT EXCEEDING SIX MONTHS OR TO A FINE NOT EXCEEDING LEVEL 5 ON THE STANDARD SCALE, OR TO BOTH.
(2) ANY PERSON WHO, NOT BEING A CONSTABLE, WEARS ANY ARTICLE OF POLICE UNIFORM IN CIRCUMSTANCES WHERE IT GIVES HIM AN APPEARANCE SO NEARLY RESEMBLING THAT OF A MEMBER OF A POLICE FORCE AS TO BE CALCULATED TO DECEIVE SHALL BE GUILTY OF AN OFFENCE AND LIABLE ON SUMMARY CONVICTION TO A FINE NOT EXCEEDING LEVEL 3 ON THE STANDARD SCALE.
(3) ANY PERSON WHO, NOT BEING A MEMBER OF A POLICE FORCE OR SPECIAL CONSTABLE, HAS IN HIS POSSESSION ANY ARTICLE OF POLICE UNIFORM SHALL, UNLESS HE PROVES THAT HE OBTAINED POSSESSION OF THAT ARTICLE LAWFULLY AND HAS POSSESSION OF IT FOR A LAWFUL PURPOSE, BE GUILTY OF AN OFFENCE AND LIABLE ON SUMMARY CONVICTION TO A FINE NOT EXCEEDING LEVEL 1 ON THE STANDARD SCALE.