Lee has given me permission to publish his email which has been edited slightly for clarity.
"My name is Lee Castleton. I am a former subpostmaster. I am writing to give you my sorrowful experience of dealings with Post Office Ltd. I believe I am the only person to have defended a civil case (and lost) for losses in my branch - Marine Drive Bridlington. Case number HQ05X02706 in the High Court London. I was taken there in Dec 2006 by Post Office Ltd.
"In Jan 2004 My Post Office branch started to accrue losses. The first of which was £1103.68. This I paid. But I telephoned helpline and explained that I lost £1103.68. They told me to pay it and it would no doubt turn up the following week as a mistake on my part. The following week we again misbalanced. I was £4300 short. Again I made the phone call to helpline but I was given no help.
"I explained I had paid in a large amount the week prior and I could not afford to pay. I was told they would look in to it. Over the following 10 weeks we misbalanced every week. Sometimes we had too much money but more often we had too little. I was frantic. I received no help and even though I never hid any misbalances, no answers we given.
"After repeatedly voicing my concerns and begged for help (over 91 phone calls in the 12 week period) I asked for an audit. I knew this would stop the never helping attitude and force some action. I am naive. On the 23rd March 2004 I was audited. I was found to be exactly where I had told Post Office I was with respect to the misbalances (-£25000).
"I did not expect what happened next. I was suspended. I was told the deficit was against my contract and that I needed to pay the money there and then. I explained that I had told Post Office repeatedly and that I felt the Horizon system was at fault.
"I was taken through a procedure where my suspension became a termination yet still despite my pointing out faults in paperwork there was no investigation. Post Office now were not paying me and they then started proceedings to recover the supposed missing money. I was able to get representation through a legal insurance.
"Post Office delayed and delayed with letters back and forth. All the time eating up the insurance money.
"Finally we went to court in Dec 06. The Post office offered little evidence other than my signed accounts. I lost. From Jan 07 to this day my family and I have suffered far beyond anything I could explain.
"I had to declare myself bankrupt because the Judge order costs against me to the value of £321000. The Judge told the Post Office that it was unlikely I would be able to pay prior to the case being heard but Post Office wanted to continue. So Post office Ltd paid £321000 to try to recover £25000. Even though they knew I could not pay.
"What is still painful is even more so when new revelations are revealed by others on a daily basis. I always asked for help and explained and reported any losses. It is not reasonable to think that an average working man can just pay ever more money into a system that clearly is flawed.
"I have documents that prove the system does not work. One of which is the one Shoosmiths refer to - the Horizon records transactions whilst the person whom the Horizon says is operating the system is not even logged on to the system. This is one of the faults from my office.
"Post Office's case against me was argued on the basis that an account stated is an account owned. They argued that I signed of the accounts as a true reflection of the the accounts. Firstly over the 12 week period I made 91 phone calls asking why the system was showing shortages or gains.
"Secondly I have now found out that Horizon has 3rd party access. Which Post Office deny. How can I own an account that a third party can change?
Since emailing this letter, Lee has asked Humberside Police to investigate his situation. He is alleging the Post Office:
"withheld the fact that the system has had and continues to have balance problems where transactions are lost. They withheld information during disclosure and still deny that the system has serious flaws with balancing.
"They have financially gained from the non-disclosure and continue to deny they have a problem with the system. They have sought to criminalise people where possible whilst withholding this information.
"They have profited from withholding this information. Because they are able to prosecute people without any form of checks with the CPS they have been able to continue to withhold this information to their own benefit in such cases."
Lee tells me the investigating officer at Humberside Police:
"has confirmed to me that he will be investigating the Post Office. He explained that he felt there is clearly a problem that needs to be looked into.
"Whilst he also felt that it will be particularly difficult to do so he feels that it is certainly something that needs to be investigated."
I ought to point out, just in case any of the Post Office's lawyers are reading this, that the Post Office believes its Horizon interface to be "robust", and no one has ever offered any testable proof that the Horizon system has any faults whatsoever.