The K8 booth, introduced in 1968, was designed by Bruce Martin. It was used primarily for new sites; around 11000 were installed, replacing earlier models only when they needed relocating or had been damaged beyond repair. The K8 retained a red colour scheme, but it was a different shade of red: a slightly brighter “Poppy Red”, which went on to become the standard colour across all kiosks.

The K8 featured a single large glass panel on two sides and the door. While improving visibility and illumination inside the box, these were vulnerable to damage. There were two versions – the Mk1 and the Mk2 – with the most visible difference being in the detail of the roof and the surround of the ‘TELEPHONE’ opals.