Retailers continue to get in touch over what they claim are unexplained PO losses through the Horizon epos system. Balbir Singh Bassi, from Oldbury in the West Midlands, who describes himself as "coming from a bookkeeping background" had an £800 loss one week, £1,400 the second week and £3,000 by the third week. The PO took it out of his wages.

"We started monitoring then," says Balbir. "We had another £2,000 loss and then it corrected itself the next day."

So could it be a phantom? David Proud emailed: "I, too, have had deficits on Horizon that I have not been able to identify. I have spent hours going through reports trying to identify the problems, but the reporting system is not at all user friendly and I find it nigh on impossible to determine what has gone wrong.  The times that I have asked the help desk for advice it has proved useless. Since I started five years ago I have had a few days with some big deficits - for example, £500 - for which I have been totally unable to solve. This has left me mistrusting the system, but also myself and staff."

He adds that checking involves printing out every transaction on the day and then sitting at a computer screen and watching every transaction being processed on the CCTV playback and comparing it with the printout. Extremely tedious.

"In terms of a solution I would like to be able to download a file of all the transactions during the day and feed this into a spreadsheet, which I could then use to analyse as an audit trail and hopefully verify totals.  I have not asked the Post Office for such a thing as I am more likely to win the jackpot on the lottery than to get such a request agreed."

He concludes that he awaits the new Horizon system with very mixed feelings. "If only we had some people at head office with experience outside the Post Office we might have a chance."

An anonymous ex-sub-postmaster told me that he had to sell his office at a loss of £50,000 to pay off a £22,000 'debt' and another claimed to have lost £28,000 overnight.

You have to be really good with figures to be a sub-postmaster. If you were seriously going to 'do' the PO would you just sit there and wait for them to come and get you afterwards?

The national media has expressed an interest in this, but the company I spoke to asked me not to identify them as they don't want their rivals to know what they are investigating.