Maybe you did not know, but the UK, too, is full of superstitions, mystical and just strange things. The tradition to say "Rabbit", "Rabbit, rabbit" or even "Rabbit, rabbit, rabbit" on the first day of the month has already spread throughout the world. The point is that if you say this word on the very first day of the month, it will be filled with luck and prosperity. It isn't known where this originates from exactly. There are many versions. Some relate back to the XV century, others to the 13th. Why a rabbit? Many attribute this to the rabbit's foot, which brings good luck, as many believe. Others say that a word, like the rabbit itself, jumps far into the future and brings good luck from there. Surely there are many other versions that exist, but many still say the word "Rabbit" just in case.
Also the British are wary of the crows in the Tower. The birds settled there in the XIX century, and the legend says that if the crows of the Tower of London fly away, the crown will fall and Britain will fall with it.