From time-to-time there are Statute Law (Repeals) Acts intended to tidy out dead wood from the massive so-called 'statute book.' (See the 2013 Act). A few candidates for the next such Act appear in the document.
It is illegal to:
Enter Parliament wearing a suit of armour; to be drunk on licensed premises; to carry a plank along a pavement; to be drunk in charge of a horse and to fire a cannon within 300 yards of a dwelling house. It is definitely illegal to kill a Scotsman in York whether within or outside the city walls and regardless of the day of the week !!
It is legal to:
Die in Parliament (and some have); eat mince pies on Christmas Day; put a stamp upside down on a letter.
A fascinating insight into some of the things which have been considered unlawful during our lengthy legal history and to some of the myths which are mentioned occasionally !
In English Law, once a statute is enacted it will always remain in force until repealed and this is so irrespective of whether the statute is actually enforced. There is no rule of desuetude.