The United Kingdom’s postal codes, known locally as postcodes, are a deceptively simple alphanumeric system that has become an essential aspect of British identity. These codes do more than just ensure mail delivery efficiency—they encapsulate the history and structure of individual houses and the broader British landscape.
Conceived by the Royal Mail between 1959 and 1974, these postcodes have evolved into tools beyond their original purpose, now used for everything from calculating insurance premiums to planning routes on GPS software. A full postcode, known as a “postcode unit” has two alphanumeric. The first alphanumeric code (the Outward code or Outcode) has between two and four characters and the second (the Inward Code or Incode) always has three characters.
For instance, a postcode such as GU22 pinpoints not just the town of Woking but navigates even further to a particular street or house within that town. The numbering system within these codes is also quite telling, revealing how postal districts are organized geographically, often from the central town outward. The numbered postal districts often infer the centrality of an area within its covers a large part of Central London south of the Thames whereas SE2 covers Abbey Wood at the far end of the Elizabeth Line.
Further intriguing are the ways these codes intersect with history. The London post town, for example, had been divided into postal districts since 1857, a system that would later be subdivided and extended to other cities in the UK, reflecting the organizational changes brought on by wartime measures and later technological advancements. The integration of older postal districts within the national postcode system has also meant that historical postal identities have been preserved and can still be seen on older street signs.
The data within the Postcode Address File (PAF) database is a treasure trove for historians and architects, storing the full address data of approximately 29 million addresses. This information forms a detailed canvas of the UK’s architectural journey over time. The adaptation of the postcode system into national data has ensured that historical postal codes live on, serving as markers that connect the present with the past.
Postcodes, therefore, are not just utilitarian components of the British postal system but keyholders to the understanding of individual houses, streets, towns, and cities.
Relevant articles:
– Postcodes in the United Kingdom