Middlesex Day is observed in England every May 16 to celebrate the history and cultural heritage of the historic county of Middlesex. This day commemorates the anniversary of the Battle of Albuera, fought in Spain in 1811, where the 57th West Middlesex regiment participated. The name "Middlesex" translates to "territory of middle Saxon," reflecting its original inhabitants, and it has a rich history dating back to its first recorded mention in 704. Over the centuries, Middlesex transitioned from part of the Kingdom of East Saxons to the Kingdom of West Saxons, and later became an administrative entity alongside London. The county's economy was historically tied to London, providing goods like grain and building materials, and it underwent significant urbanization in the 18th and 19th centuries. Although Middlesex was incorporated into Greater London in the 1960s, Middlesex Day serves as a reminder of its legacy and the bravery of its soldiers.