Artist Harriet Russell decided to see how dedicated the mail carriers in the United Kindgom really are. She sent 130 letters to herself and obscured the address with ciphers, puzzles, and cryptograms. Turns out those Royal Mail carriers take their jobs very seriously; only 10 letters were not delivered.
The designs and ciphers were of varying complexity and tested different areas of perception, including color-blindness. Russell worried a bit that she might get in trouble with the authorities for wasting their time. From an interview in The Independent:
"I was really quite amazed. I didn't know who was doing it. I imagined there was a small group of them and I think they must have caught on because a lot of them were to the same address."
And incredibly, Russell didn't realize that she was following in the footsteps of a family tradition of encrypting postal addresses. From the same interview:
In another pleasing twist to the story, Ms Russell was unwittingly resurrecting a family tradition first begun by her great-great grandfather Henry Ponsonby, a private secretary to Queen Victoria and a veteran of the Crimean War. This eminent forebear embellished letters to his children at Eton with a series of illustrations in which he concealed the school's address. It was a family quirk continued by his son, Arthur Ponsonby, a pacifist who went on to be Labour MP for Sheffield Brightside before his elevation to the House of Lords.