The Law states that private hire should be pre-booked. Indeed, our beloved council even arranged for a sticker to be placed on the front doors of PH cars, because this would prevent vulnerable females, including those under the influence of drink and drugs, from being raped. Quality!!!
How comforting to know how much our council cares about the public, rather than naked commercial greed.
Anyway, like "fit and proper" and "as it sees fit" the council is not bound to define what "pre-booked" is. it doesn't appear in licensing conditions and, surprise surprise, the CGSA doesn't define it either (the Act was not crafted for the current commercial reality, and the Scottish Nasties won't review it because it protects control and their commercial pals.)
So, technically, one could approach a PH car, you could say, "Can I book you to take me to ..... in one minute?" and the driver could fone in, log the job in the system and take the fare.
The reality of course is that the driver is self employed. Being less than three cars in his business, he doesn't come under base licensing. There's nothing to stop him saying, ring my mobby, and jump in.
Of course we know, it's really just a signoff from the circuit (for a natural break of course

well it is natural to put self interest first, isn't it?), jump in and meter on, or fare by agreement.
Do you think our politically corrupt council and morally bankrupt Scottish Nasty government don't realise this?
Woodburn, Cardownie, MacAskill, Salmond. Says it all does it not?