Recently I invented a new game. It’s called Xanadu, after Kubla Khan’s legendary summer palace and of course, the film Citizen Kane. The rules are simple. You walk, cycle or drive in your local area, bagging as many black-on-yellow signs – the ones pointing to new housing developments – as possible. There are two prizes – the one who gets the most signs and can remember their names and one for the most ridiculous – not as easy as…