So one assumes the driver didn't go and read the sign. If you were the driver, you can tell us because the driver has no role in the enforcement process, it is all down to the registered keeper.
Basically, if one parks in a marked-out bay, one has a duty to look for the sign controlling that bay. So at the moment, I see no winning appeal argument, but you could try submitting a non-confrontational representation saying that your driver thought the TH permit allowed parking in any bay in Tower Hamlets. Put in "awfully sorry, wont happen again" etc
Having said the above, there may be a 'technical' appeal based on TH mismanagement of the enforcement process. Such appeals usually have nothing to do with the contravention itself. Councils have duties as well as the poor motorist and if they fail to follow the enforcement Acts and regulations the PCN is usually void.
Our expert on these are 'Hippocrates' so wait a bit to see if he has anything to suggest. On the contravention itself, you look bang-to-rights.
