There are two possible avenues that could support an appeal to the Traffic Penalty Tribunal, (1) is the single No Entry sign obscured by the trees on the approach ? The council have been rather remiss in only installing one sign, and there is no advance warning, and (2), there will be PCNs dated between the date of the first PCN, and the date the first PCN was received. So by the time your friend realised his error, several PCNs had been issued. To ask for them all to be paid is quite unfair and has won appeals in the past. If he can show how the sign was not very visible, and, of course, easily hidden by a high vehicle, then this would be a credible appeal. I would suggest that to support an appeal, photos are taken of the approach to see what the degree of obscuration the trees are causing.
Of course, to take the matter to the TPT, the full PCN penalties will be in play so there is some risk, and how robust a case can be made for cancellation. If the sign is badly obscured, all the PCNs should be cancelled.
Just look at all the GSV views take in Spring and Summer. The No Entry sign is nowhere to be seen. There really should be two signs here, one on each side of the road.
https://maps.app.goo.gl/RSxSkUeiPyZpwcG18
