You did that too?
It was my older brother's biggest wheeze. I thought he invented it. That's what he told me.
I used to be lookout (well I was 6 and he was a grown-up 12).
The look on householders' faces when they stomped on the bag has us giggling like maniacs from a nice safe distance round the corner.
I'll tell him that you are looking after his tradition next time I visit him in Broadmoor.