Some time ago, I came across some fascinating academic research suggesting that people reported higher levels of happiness in an area where somebody had put up signs reading: “10 smiles an hour zone”.
I'm a sucker for this kind of thing, and decided to put up similar signs near where I live. Not wanting to make a dreadful mess, I put them on signs where I thought they more or less looked official. (Not that any official would ever put up something quite so wonky.)
I drew them on art-quality paper, and backed it with gelatine to give it an organic and compostable stickiness. Then I put them up.
What I didn't get round to doing, alas, was any kind of scientific study as to the happiness levels of my neighbours. One of them, or possibly a traffic warden, appears to have had a go at removing the sticker in this picture.
PS. After I wrote this, I was contacted by @ThePlantLondon who kindly knocked up a much more official-looking sign. Thank you!