In his book Picturing & Poeting Alan Fletcher says, "The 0 in the number 10 on the black door of the British prime minister's house at 10 Downing Street is wonky. Take a look when you next see a newsreel."
He's correct. And I know why.
It's supposed to be so that when you look down the street (from Whitehall) you see the door at an angle and the 0 looks straight. Like this.
Do you think it works?