The world’s first adhesive postage stamp used in a public postal system. It was first issued in the United Kingdom, on 1 May 1840, but was not valid for use until 6 May. The stamp features a profile of Queen Victoria.
In 1837, British postal rates were high, complex and anomalous. To simplify matters, Sir Rowland Hill proposed an adhesive stamp to indicate pre-payment of postage.
Printing of the 1d labels on watermarked paper began on 11 April and on 1 May both it and the Mulready stationery were put on sale in London, becoming valid for postage on 6 May. By then some 600,000 labels were being produced daily. The 2d label followed, printing only beginning on 1 May.
A complete sheet of the Penny Black without check letters is held by the British Postal Museum.