The traffic order is
The GLA Roads and GLA Side Roads (Hackney) Red Route Consolidation Traffic Order 2007, the relevant entry is item 15 on page 80.
Will get him to draft something and will post it here for review before submission if that's ok.
It looks like something was already submitted on Friday, can we see a copy please?
Here are the TFL photos:




Apparently the TFL warden "threw" the ticket at him while he was in the car?! 
I don't suppose he has a dashcam or any witnesses who can confirm this? Did he open the window as he was driving off, and crucially had the car started moving at the point where the PCN was thrown?
The photos show that no PCN had been served and the last photo shows the car wheels had started moving at the time when the photo was taken, this could be important but first we need a precise account of the sequence of events. If the car has a dashcam with footage of the events, that's even better. The case of
Michael Boakye v London Borough of Bexley (2200234487, 7 August 2020) illustrates the issue, but I know there is one floating around where the PCN was actually thrown through the window and landed in the driver's lap, that was also held not to be good service.
Lastly it seems this might have been a PCSO (as far as I can work out the T at the end of the CEO number indicates it's a Traffic PCSO), which opens up the uniform argument.