Anniversary of the day Charles II hid in the oak tree from the Roundhead troops, thus enabling him to live a bit longer with his head and re-establish the monarchy. We got him in the end though.Celebrated by the wearing of a sprig of oak leaves with or without oak apple. An oak apple is the hard round ball left by the gall wasp which lays it's eggs in the bark, the wasp larvae lives in this gall until it pupates and flies away out of the tiny hole it makes for the purpose.
Bet you wish you hadn't asked now....
LTS