Four of Six London Red Telephone Boxes in Smithfield Market London
The large boxes are K2s and the smaller boxes are K6s. The original design for the red phone box was the K2 but due to its size it proved to costly to produce and only a handful were installed outside of London. After a redesign of the K1, and the next design, the K3, they went back to the drawing board and came up with the K6. Smaller and easier to produce, and as the footprint is smaller too, easier to find locations to site them.