From the Pathe News archive: the UK's first licensed two-way-radio controlled taxis in Cambridge. The company was indeed called "Camtax" and a picture of its radio licence appears in one of the Chris Lorek "two way radio conversion" books.
Anyone recognise the radio gear in use? Clearly Pye - but doesn't look like the "PTC" series I vaguely recall.
One of the microphones in use in the taxi reminds me of the WWII-era "Microphones Hand" used with the likes of the WS18.
See
https://youtu.be/KvSE0HR06bE