What happened
Blair's government inherited the Horizon contract from Major — but inherited it is not the same as having no agency over it. In 1999, the Benefits Agency (then part of the DSS under Blair's government) cancelled its participation in Horizon. The original contract had two components: benefit payment automation and Post Office accounting. The Benefits Agency pulled out, in part because of concerns about the system.
The Post Office — still a public corporation under government oversight — decided to press ahead with its accounting component regardless.
This is the moment nobody has adequately answered for: Blair's government had a signal in 1999 that something was wrong with Horizon. One arm of the state acted on it. Another arm — the Post Office, whose board was appointed by ministers — did not. No minister appears to have asked why the Benefits Agency was walking away from a system the Post Office was simultaneously betting its prosecutions on.
Subpostmasters reported discrepancies almost immediately after rollout: • The system showed shortfalls that subpostmasters could not explain or reproduce • The Post Office helpline told them the system was infallible and the fault must be theirs • Fujitsu's own engineers had internal bug reports documenting software defects from the earliest deployments • None of this information was disclosed to defendants
The first wrongful conviction came in 2000. By 2005, dozens of geographically dispersed individuals had been convicted for the same pattern of 'unexplained shortfalls'. The pattern was either not noticed or not acted upon. No minister asked why subpostmasters were suddenly committing fraud at unprecedented rates.