The Common Issues trial examined the contract between the subpostmasters and the Post Office and found largely in favour of the claimants, while the Horizon Issues trial found that Horizon, the Post Office's accounting software, contained bugs, errors and defects that could cause shortfalls in the subpostmasters' accounts.

[a] In 1999 the Post Office rolled out new electronic point of sale and accounting software, Horizon (produced and maintained by Fujitsu), to its network of over 11,000 branches.

[1] Soon after the installation of Horizon, subpostmasters started to experience unexplained shortfalls in the accounts, which, under the terms of their contracts, they were expected to make good with their own money, leading to debt and, on occasion, bankruptcy.

Under pressure from the JFSA and a group of Members of Parliament (MPs), led by James Arbuthnot, the Post Office in 2013 appointed forensic accountants Second Sight to investigate Horizon prosecutions.

[9] Referring to costs and delay, the judge said, "Fitting hearings around their availability has all the disadvantages of doing an intricate jigsaw puzzle, with none of the fun associated with that activity.

"[6] This decision followed a case management hearing and dismissed an application to strike out roughly one-quarter of the lead claimants' evidence – more than 160 paragraphs.

[10] The judge commented that adverse publicity for the Post Office was not a matter of concern for the court if the evidence was relevant and admissible.

Referring to Angela van den Bogerd (Head of Partnerships at the Post Office), the judge said: "[she] did not give me frank evidence, and sought to obfuscate matters, and mislead me.

[15] The Post Office brought in Lord Grabiner to make an application to Justice Fraser that he recuse himself on the grounds of apparent bias.

He sympathised with the view of the subpostmasters that the application for recusal had been intended to lead to the collapse of the Horizon Issues trial, although he did not reach any conclusions on the point.

[12] The Post Office asked for the costs to be reserved until the end of litigation, as they claimed that an interim decision "would demonstrate a pre-determination as to the overall outcome".

[12] Justice Fraser found that bugs, errors and defects in Horizon rendered it unreliable and had the potential to cause discrepancies in subpostmasters' accounts.

[20] He was critical of the Post Office's evidence, describing it as "bare assertions and denials that ignore what has actually occurred... [amounting] to the 21st century equivalent of maintaining that the earth is flat".

[21] When details were made public in August 2020, it emerged that one condition of the agreement had been the setting up of a compensation scheme for all those subpostmasters (not just the 555) who had suffered losses due to Horizon.