I thought I'd read it somewhere.... it's part of the terms and conditions which e-tagged sheep sign when they register:
"If we send a notice to you by registered post at your address, we will be allowed to
treat it as if you have received it 10 calendar days after we posted it. This means we do
not have to prove that you did receive it after 10 calendar days."
what a flippen cheek, but tagged people probably deserve this.... and vaseline