Ah, back in the days when telephones had a wire coming out of the talking-end attaching them to a box with a circular dial, British Telecom (then known as 'The General Post Office') commissioned a competition in 1924 to design a public cubical to replace their concrete 'K1' kiosk.
The winning 'K2' design by Giles Gilbert Scott satisfied the GPO and the Royal Fine Arts Commission as to its suitability and was produced in red painted cast iron and glass. This design was subsequently superseded by designs K3-K8.
Many have now been removed, converted into useful street-urinals or kiosks in which one can browse the local massage services on offer.
Design at SoVibrant. www.sovibrant.co.uk