Can the authorities involved in the British Post Office scandal be subject to charges of malicious prosecution or similar?

Question

The British Post Office Scandal is a hot topic in the news due to a recent TV dramatization, and because many cases are shockingly still open even though they date back to 1999 and are/were based on prosecutors pushing what are now universally (?) acknowledged to be spurious claims and false 'facts'.

As Wikipedia summarizes

The British Post Office scandal saw 3,500 subpostmasters accused of stealing money from the Post Office when shortfalls at their branches were in fact due to errors in the Post Office's Horizon accounting software. Between 1999 and 2015 over 900 subpostmasters were prosecuted...The court cases, criminal convictions, imprisonments, losses of livelihood and homes, debts and bankruptcies took a heavy toll on victims and their families, leading to stress, illness, divorce and, in at least four cases, suicide.

The BBC called the convictions "the UK's most widespread miscarriage of justice".

It appears from news reports that the scandal dragged even after high level administrators were informed on multiple occasions that the cases were problematic due to unreliable evidence, but that prosecutions continued unabated anyway.

Is it possible for victims of this tragedy to sue authorities for malicious prosecution, abuse of or lack of due process, or on some similar basis? What seems to have gone on here went beyond mere incompetence and into a sort of denial of reality as prosecutors repeatedly ignored exonerating facts across hundreds of cases. It boggles the mind that this is compatible with the basic ethics of any legal bodies / regulators involved.

If such legal action is possible, can the persons involved be held personally accountable or do they have some sort of qualified immunity in this kind of case?

What is the role of "private prosecution", which was at play here, in the answer to these questions?

Answer 1

Yes, it is possible for victims of the British Post Office scandal to sue the authorities for malicious prosecution. In fact, this occurred in the civil litigation which brought the scandal to light, after which the recent TV series was named. Bates v Post Office was a High Court group action commenced by some 550 former subpostmasters in 2017. Not all had been prosecuted by the Post Office, but those who had been sued for the tort of malicious prosecution, among other financial claims: Bates & Ors v Post Office Ltd (No 3) (Common Issues) [2019] EWHC 606 (QB) [10].

On 10 December 2019, the group action was settled on terms which provided for the Post Office to pay £57.75m, and the claimants to give up their claims other than claims for malicious prosecution by convicted claimants. While the Post Office did not oppose the quashing of the convictions in separate criminal appeal proceedings, they denied that they were liable for malicious prosecution because at least some of the prosecutions were justified by evidence unrelated to the flawed Horizon system, including confessions. It was left to these convicted claimants to pursue their criminal appeals and, if successful, commence a fresh civil action for malicious prosecution. Most of the group action settlement funds were then consumed by legal fees, so the unhappy subpostmasters intensified their public campaign for other means of exoneration and compensation, including for subpostmasters who did not participate in the group action.

On 29 September 2020, the Post Office Horizon IT Inquiry was established. On 10 January 2021, it was reported that further claims for malicious prosecution will be filed. On 9 May 2022, the Inquiry published its view on Compensation Issues relating to Prosecuted Sub-postmasters, which reviewed some of the difficulties associated with malicious prosecution claims and the extra-judicial compensation schemes that have now been established. It has also been reported that the police are investigating potential offences of fraud, perjury and perverting the course of justice. It remains to be seen whether these processes will lead to the Post Office, or its individual agents, being held liable for malicious prosecution or related criminal offences.