Barnet Council behaviour is inexplicable

Not Mr Mustard's description but that of a long serving (and occasionally suffering) adjudicator:

A restricted street is one with single or double yellow lines.

 

It wouldn't be wise in Greater London, or indeed in most urban areas, to leave a vehicle boot open whilst loading or unloading. If your delivery is out of sight of the car, as one can't always park right outside, then of course a traffic warden won't see any loading/unloading activity. That does not mean it is not happening.

If the council reject your loading/unloading argument you will have the ebst chance of winning at the tribunal if you go there in person (treat it like a fun day out, Mr Mustard has one every week) as then your honesty can be tested by the adjudicator and the council will rely only on the paper evidence so cannot dispute what you have to see on the day.

Good luck.