This has been widely reported.
Yes, there was a rogue sign (placed there apparently by an unauthorised member of the public in what the police are investigating as an attempt to pervert the course of justice), but the problem for all the drivers claiming that it caused them to speed is that such a claim is nonsense.
That stretch of road has average speed measuring cameras. The fake sign was close to the second camera, and if you do the maths it's impossible for any driver's average speed to have exceeded the threshold for prosecution if they accelerated to 50 when they passed the sign if they'd been driving at the correct speed before it.
Any driver who got a speeding ticket had to have already been speeding past all the 40mph signs before the 50mph ones.
It may be that even though that section of the A20 was correctly signed when a temporary speed limit was put in place, the presence of the sign invalidated the entire traffic order until it was removed, but that's the only grounds for appeal anybody has - saying "I wouldn't have been speeding if that sign hadn't been there" is demonstrably untrue.
