In researching the cost of sending a letter-size envelope to London ($.80, so now you know), I stumbled upon a page detailing Country Conditions for Mailing – Great Britain and Northern Ireland. I will quote the prohibitions and restrictions in full:
Any postal item containing enclosures addressed to different persons at different addresses.
Arms and parts of arms, except as noted under Observation #5 below.
Articles, goods infringing British trademarks or copyright laws.
Cards decorated with mica or ground glass or similar materials unless they are placed in envelopes.
Citizens Band Radios, walkie-talkies, microbugs, and radio microphones that are capable of transmitting on any frequency between 26.1 and 29.7 megacycles per second and 88 to 108 Mhz per second.
Goods made in foreign prisons, except those imported for a non-commercial purpose or of a kind not manufactured in the UK.
Horror comics and matrices.
Obscene articles, prints, paintings, cards, films, videotapes, etc.
Perishable infectious biological substances.
Seal skins except those from an accepted source.
Coins; banknotes; currency notes (paper money); securities payable to bearer; traveler’s checks; manufactured and unmanufactured platinum, gold, silver; precious stones; jewelry; and other valuable articles, may only be sent in registered letter-post shipments or insured parcel post.
Foods or beverages to which any preservative or other substance has been added must comply with the British regulations for importation.
Live queen bees must be accompanied by an import license issued by a UK Government Agricultural Department and a health certificate issued by the appropriate Government Department of the country of origin stating that the bees are free of disease.
Meat, meat products, and animal products including dry sausage and dried milk require import license issued by appropriate UK Agricultural Department.
Plants and parts of plants require import permit issued by the appropriate Agricultural Department in UK.
That, my friend, is Comedy Gold. I see Harper’s mined it as such a couple of years ago.
Oh, and if you were wondering what horror matrices are (as I was), M-W tells us that, a matrix is (among other things)
2 a : a mold from which a relief surface (as a piece of type) is made b : DIE 3a(1) c : an engraved or inscribed die or stamp d : an electroformed impression of a phonograph record used for mass-producing duplicates of the original