If you were to show this picture to people and ask them what it is, the vast majority would tell you it's a Tardis? Perhaps more than any other object, a popular TV programme has completely transformed the public perception of this once-familiar feature of British cities.
That programme, of course, is Doctor Who, the seminal British sci-fi series first aired in 1963. The Doctor is a Time Lord from the planet Gallifrey who travels through space and time in his TARDIS – an acronym for Time and Relative Dimension in Space.
The Tardis is designed to change its outward appearance to blend in with its surroundings wherever in time and space it might land. Unfortunately the Doctor's Tardis has a broken "chameleon circuit" meaning that it remains stuck in its last guise – that of a Police Public Call Box, a relatively common sight when Doctor Who first screened on TV.
So what this picture actually shows is a Police Public Call Box, introduced in London in 1929 and now a very rare sight. Of the 1,000 installed, there are thought to be only 11 remaining, no longer in use but preserved as part of the UK's architectural heritage.
As Britain's public telephone network developed it was decided that major cities should have these 'newfangled' means of communication to help in the fight against crime. The police box allowed constables to contact their station while out on the beat, and members of the public to raise the alarm in an emergency.
The earliest examples were introduced in Glasgow in 1891, painted red. But the best known design, and the one copied for the Tardis, was the London Metropolitan Police Box, designed by Gilbert Mackenzie Trench in 1929 and painted dark blue. Around 685 of these police boxes were introduced in London and more than 320 in Glasgow.
While the GPO's iconic red public phone boxes were made from cast iron and glass, the police box was built in concrete, not wood as many people imagine. The only wooden part was the teak door, with the rest made from pre-cast concrete panels fixed to four thick concrete corner posts, designed to withstand impact by a vehicle as well as fire.
During the blitz it wasn't unknown for constables to squeeze people into a police call box like sardines in a tin if they couldn't reach to the nearest air raid shelter in time. Unfortunately, unlike The Doctor's Tardis, the real police call box is not bigger on the inside!
Each side of the police box has two metal-framed windows, with one of their six glass panels tinted cobalt blue, like the old lamps outside police stations. The right hand half of the police box front is its narrow teak door, through which only police officers could enter with a key. They were designed to be almost a mini police station – a place where a beat constable could take a short break, shelter from very bad weather or make notes in his pocketbook.
Inside were a small table with a drawer, a stool, a fire extinguisher and first aid kit, a broom and a small electric heater. The public telephone was accessed from outside the box, stored in a recessed box set into the left front panel, behind a hinged door. People only had to open the door and lift the receiver to speak directly to the police station.
Behind a larger door in the panel below the phone was a first aid kit, again for use by the public in an emergency. They had to break a small glass panel to get the key to open the door. The London police boxes had a tiered concrete roof with a light on top which would flash to alert any passing constable that he needed to contact the station.
As radio communication technologies developed in the 1950s and '60s, and more officers used patrol cars, the police boxes became increasing obsolete. By now there were also thousands more public phone boxes with the free 999 emergency call option.
In 1969 it was decided to start decommissioning the old police boxes, either dismantled or demolished on site. London's last police box was removed by 1981 and of the 1,000 Mackenzie Trench police boxes installed between 1929 and 1938, less than two per cent survive, mainly relocated to heritage museums.
However, the enduring popularity of Doctor Who has seen a rash of replica boxes built at various tourist attractions, offering visitors the chance to have their picture taken next to a "Tardis".