Coals to Newcastle

Selling, carrying, bringing, or taking coal(s) to Newcastle is an idiom of English origin describing a pointless action. It refers to the fact that, historically, the economy of Newcastle upon Tyne in north-eastern England was a great center of coal shipments from nearby mines, and therefore any attempt to sell coal to Newcastle would be foolhardy as supply would be greater there than anywhere else in Britain. Similarly, Newcastle, New South Wales (named after the northeastern city) has one of the largest coal ports in the world, and hence it would also be meaningless to ship coals there.