Blue and Red post boxes at Windsor Castle in Berkshire, England. The Blue post boxes were for airmail letters and placed at important sites, they only lasted for eight years because of the rapid expansion of air services to Europe and the British Empire their usefulness was made redundant
Nicknamed the Vermillion Giant, the K4 was a combined telephone and post box with stamp vending machine. The design was introduced in 1927 but they proved unpopular with customers. Only 50 were ever produced and most were withdrawn in 1935. However, around 10 survive in the UK including this one in Whitley Bay, Tyne and Wear.