Transparency has always been lacking at the Post Office, Ministers must make it accountable to everyone - David Behrens

It’s what television, in the right hands, has always been good at. In 1966 there was spontaneous and genuine public anger when Ken Loach’s Cathy Come Home exposed the appalling reality of a social care system that cared for no-one and nothing. It could not be ignored and it brought immediate change. Mr Bates vs The Post Office on ITV last week is having a similar effect.

The convulsion of public anger it set off – uncoincidentally in an election year – has awoken complacent politicians to the need for action they should have taken long ago. Good.

But it’s worth looking at just how little was being done before last week to put right what was already being called the biggest miscarriage of justice in British history – and after Hillsborough, Windrush and the Guildford Four that’s quite a high bar. Yes, there has been a public inquiry in which those who orchestrated the misery have sought to hide behind confidentiality clauses and lapses of memory, but back in their offices business has been going on entirely as usual.

Specifically, government departments have continued to hand lucrative contracts to the Japanese IT firm whose defective software caused the whole debacle in the first place. Fujitsu, architect of the miserable Horizon accounting system – which, by the way, the Post Office still uses – will earn close to half a billion pounds from new deals to service the Foreign Office, HMRC and the police national database.

Those figures were obtained by the magazine Computer Weekly, which has been investigating Horizon since 2008. The fact that Fujitsu was not blacklisted at that time by government buyers pending a satisfactory compensation deal for the wrongly convicted postmasters demonstrates just how little importance was attached to their suffering.

Then there’s the sanctimonious Paula Vennells, ineffective former boss of the Post Office on whose watch the organisation moved heaven and earth to conceal the reasons for its malicious and dishonest prosecutions. Realising the game was up, she handed back her CBE this week – having declined to do so for the previous five years – but has failed to come clean about what she knew and what she did about it.

Did she as head of the organisation know Horizon was as faulty as her subpostmasters said it was? If not, it can only have been because she failed to ask the right questions of her subordinates and that makes her incompetent. If she did know and failed to say so, it makes her a sinner – which rather compromises her other position as a minister in the Church of England.

Her boss in that role, the ludicrous Bishop of St Albans, was a lone voice in her defence this week, citing the nebulous argument that Mr Bates vs The Post Office “diverges from actual fact into TV”. The church is as deaf to public opinion here as the rest of the establishment; at the height of the Horizon scandal it shortlisted Vennells to be Bishop of London, for heaven’s sake.

But what is most unjust about this unholy saga is the archaic right the Post Office retains to investigate and prosecute crimes within its business without any reference to the police or elected officials. The conflict of interest as both the aggrieved party and supposedly impartial advocate is fundamentally unsafe.

I know just a little about what it’s like to be caught up in this opaque system because in 2009, as word of the Horizon scandal first emerged, the Post Office rubber-stamped an application with my forged signature to redirect all my mail to a terrace in Oldham whose occupants then ran up a £7,000 bill on credit cards they obtained in my name.

The application form, which I later saw and have kept, didn’t stand a moment’s scrutiny but I was never allowed to know what really happened because the investigation – if there was one – was ‘confidential’.

I was lucky; the money was written off quickly though it took longer to purge my credit record. But I knew then that the Post Office was a legal wilderness in which justice was neither done nor seen to be done.

Now we all know. And ministers must seize this rare moment of revelation to sweep away the secrecy from an institution we all own and make it accountable to everyone.