In 1977 it was the Queens Silver Jubilee and I was six. At the time my grandfather was a salesman for a lingerie and nightwear company and often came home with free samples for us (nasty nylon stuff it was too!). Just before the Jubilee he brought my mum home a pair of Union Jack knickets.
Anyway - week before the Jubilee - Sunday School - children are invited to come up to the front to tell the others what they are doing for the Jubilee. I had been nattering my mum for days about this and she refused to tell me what was planned (street party, basically) - but told me what she was going to do. Unfortunately I believed her - and told the Sunday School that my mummy was going to run up and down the road wearing nothing but her Union Jack knickers ...
(... and if that wasn't bad enough, my mum played the piano for Sunday School so she was sitting in the room at the time - don't think she lived that one down for years ...)