Is this bit true? "The registered keeper
was not that driver and cannot be presumed to have been, nor pursued under some twisted interpretation of the law of agency."
There is no need to lie. You need to understand that the keeper and the driver are two separate entities in law. You can be either, both or neither.
MET does not know who the driver is unless the keeper tells them, inadvertently or otherwise. There is no legal obligation on the keeper to identify the driver.
So, you are appealing as the keeper, irrespective of whether you were also the driver or not. You are not required to admit to being the driver. This is not a criminal matter where that obligation is different. This is civil matter.
So, please simplify that appeal to this. No need for embellishment or lying:
I am the registered keeper. MET cannot hold a registered keeper liable for any alleged contravention on land that is under statutory control. As a matter of fact and law, MET will be well aware that they cannot use the PoFA provisions because Stansted Airport is not 'relevant land' and BP Stansted in on that land.
If Stansted Airport wanted to hold owners or keepers liable under airport bylaws, that would be within the landowner's gift and another matter entirely. However, not only is that not pleaded, it is also not legally possible because MET is not the Airport owner and your 'parking charge' is not and never attempts to be a penalty. It is created for MET's own profit (as opposed to a bylaws penalty that goes to the public purse) and MET has relied on contract law allegations of breach against the driver only.
The registered keeper cannot be presumed or inferred to have been the driver, nor pursued under some twisted interpretation of the law of agency. Your NTK can only hold the driver liable. MET have no hope at POPLA, so you are urged to save us both a complete waste of time and cancel the PCN.