Once heard an interesting talk from a guy at the patents office in Newport. He claimed that German bomb fuses, being very clever, had been patented. EOD, or their equivalents of the time simply went to the patents office and consulted the drawings. Having said that he also had a story about and intelligent cat flap patent being turned down because walter the softy’s dog had been illustrated using one in an old issue of th Beano. If it’s been thought of before you can’t patent it.