Several designs from companies and architects were entered.
It was 1926 when the chosen design appeared, Sir Giles Gilbert Scott's K2.
Bruce Martin was the winning architect and his design appeared in 1968. The main differences were that the glazing bars had gone to be replaced with just 1 big window on each side of the kiosk and the domed roof was replaced with a much flatter design.
It was nicknamed the Vermillion Giant and was a fantastic failure. In 1934, a K5 was produced, made of plywood as a temporary kiosk for use at exhibitions and fairs etc..
For a brief time, the K8 was painted yellow but this didn't last and they were soon returned to red.
Vandalism was always a problem with telephone boxes and during the 70s British Telecom made another modification to the K6, many kiosks had their glazing bars ripped out and had a single piece of glass put in like the K8.
Nobody could deny the fuctionality of the designs as their main objectives were to be easy for disabled people to use and very easy to maintain, but everybody could deny the attractiveness of the designs.
In the late 90s, BT made an attempt to win the public over to the KX range by introducing the KXPlus which is basically a KX100 with a red bar round the sides and a domed red roof.
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Another design was tried out for areas where kiosks suffered extreme vandalism (boxes set on fire and some ripped out of the ground altogether!