The K4 was not a Scott design, although outwardly its appearance owes much to Scott's triumphant K2 design. In fact the K4 was designed and produced in-house within the Post Office engineering department. Introduced in 1927, the K4 was half as large as a K2 again and attempted to combine a telephone kiosk with a Post Office; the first full-automated twenty-four hour postal service. At this time the Post Office was responsible for the majority of the UK's public telephone network and held a monopoly on postal collections and deliveries.
The K4 kiosk was rectangular in cross-section, the longer side sported an illuminated sign saying "Post Office" one shorter side "Stamps" and above the door "Telephone". Behind the kiosk there were two stamp machines and a postbox, illuminated by a lamp attached to the an elongated K2 domed roof.
If the K2 had a large footprint, the K4 was monolithic. It was christened the "Vermillion Giant" as it proved too large for many streets; the stamp machines were excessively noisy during telephone conversations and the machines were not weather-proof which caused problems with the adhesive on the stamps. Ultimately the design for the K4 proved unsuccessful and only fifty were ever produced.
