The ducks in St James's Park are so used to being fed bread...

The ducks in St James's Park are so used to being fed bread by secret agents meeting clandestinely that they have developed their own Pavlovian reaction. Put a St James's Park duck in a laboratory cage and show it a picture of two men -- one usually wearing a coat with a fur collar, the other something sombre with a scarf -- and it'll look up expectantly.