An obvious trap for the motorist that must be a nice little earner for Newham. However you do need to be much more alert if you're going to park in London. The double-yellow lines and the absence of a bay sign are big warnings, or should be. In any big city, but especially London, with its PCN penalties double the rest of the UK, if it looks to good to be true, then it IS to good to be true.
I'm not sure what to suggest, because I can't see any obvious appeal argument, so wait until more London-knowledgeable folk have contributed. However don't miss any deadlines on the PCN !