There are the remains of an old Roman fort (Melandra Castle) near where I live. One April 1st, the local newspaper ran a story about some children who had come across some valuable artefacts (statues, coins and so on) while playing there. These all commemorated the fort's governor, one "Aprilius Primus", who died in 55 BC.

Unfortunately, some of those nearby residents who didn't spot the April Fool (there were a lot of them; Melandra Castle backs onto a council housing estate), caused some damage to the site, using metal detectors and shovels to try and find more bits and pieces of value.