What are these stickers, currently to be seen on many cars in London reading "Pre-booked only" and "PRIVATE HIRE" (inside a blue version of the familiar London Underground bar and roundel logo)? They indicate that the cars are minicabs.
Regulation of the minicab trade in London was delayed for thirty or so years because the black cab trade, vociferously represented by the LTDA tried to pretend that minicabs did not exist. Eventually the Private Hire Vehicles (London) Act 1998 was brought in. But the LTDA's influence was strong: Section 31 prohibits the use of the terms 'taxi' or 'cab'. In the next paragraph it allows (reluctantly one feels) the term 'minicab'.
Parliament had discussed the matter of signage on minicabs. One lady told the tale of a Japanese tourist refusing to get into a licenced hackney carriage because it was painted yellow. Another felt there should be no signs at all. It was left to the Secretary of State to make the regulations: Section 30 of the act.
The Secretary of State delegated regulation to the Public Carriage Office who had been regulating London cabs for 150 years. They decided that that this discrete disk about 12 cm in diameter was sufficient.
Congestion Charging was no problem - all minicabs are recorded in a database and they were automatically exempt.
It rankles heavily with the minicab trade that they are not allowed to use bus lanes like black cabs are nor were they allowed to even stop on a red route to set down or pick up passengers. On this latter point, Transport for London relented and agreed that minicabs should be allowed to stop. The question then arose: how do we identify minicabs.
Apparently the "discrete disk" was insufficient despite the fact that they are placed on the front and rear windows. Even more strangely, the database of registration numbers was apparently not available to the red route enforcers. So the slightly bigger and more prominent "Pre-booked only" sticker had to be added at front and rear.
Now they are actually allowing a modest amount of further signage, like showing the cab firm's name and phone number!