I'd look at this a different way, not in terms of the licence rules. If you are in command, albeit just for a taxi, you owe a legal duty of care to those around you, including your passenger. If something does go wrong, you need some basis on which to demonstrate that you could discharge that duty of care. Partly, it's about whether your actual experience would give you that ability. But, one would need to take account also of the need for a passenger to be with you. In other words, it would be too easy for someone to assert that a more prudent course of action would be to let go own your own. I suspect the latter circumstance is the one which could also undermine the insurance cover. If the passenger had some legitimate reason for being there, not might be different