There is no single postal code for the United Kingdom. Each area of the country has different postal codes that designate a specific area with a number of addresses.
The modern postal code of the U.K. has its origins in the postal reforms in 1840. London was the first area to get postal codes, which comprised of alpha-numeric combinations. Other large cities and towns followed. After 1960, the Post Office began a "mechanisation programme" for the sorting of letters and parcels, and the current postal codes were born. They consist of an outward code required to sort from one town to another and an inward code used for sorting within town.