The momentum has been steadily growing, but they need living proof from existing postmasters and mostly all they have are retailers of previous good character found guilty, bankrupted and imprisoned by the steamrollering legal resources available to the Post Office itself.
There certainly is proof, but the postmasters need anonymity to keep their positions. I've had various forwarded emails including complaints from retailers still experiencing problems and now the howls grow louder about glitches in the trials of the new, supposedly improved, Horizon online system.
I've also been contacted directly. The following incident involved only a couple of hundred quid, but the couple could have missed it so easily.
He told me: "A customer put his PO account number in to get £200 and the system authorised it and printed the receipt, but when he then put his wife's card in, the system crashed. When my wife balanced at 5.30pm we were £200 down. We have a transaction log and it did not show up.
"The gentleman later brought his receipt in so I could pinpoint the time, though it wasn't on the transaction log. The PO is now wondering whether that money has come out of the customer's account or is floating around in cyber space. Make no mistake, if we hadn't had proof, we would have been held liable."
He described the helpline he notified as being operated by "a bunch of numpties reading from a script" and adds: "We were on again today for 13 minutes for a minor glitch."
He credits his wife's good housekeeping for finding the error. "One penny out and she gets upset. That evening we were scrabbling around in the bins."
As there is parking outside their village PO it gets very busy with Ebay parcels. "Sometimes you get 10 or 20 parcels and the screen will spit up an error message, then it clears. You have to print up another transaction log to see if it had gone through. I rang the union and they said they are aware of it."
He also points out that customers get tired of queues and will tend to blame the postmaster. "It takes a long time to build a reputation and you can lose it in a second."