This stirring docuseries charts the rise of Larry Krasner, a crusading attorney fighting for justice in a corrupt city. And there’s no catch!

Such is the tenor of our times that the first thing I did before embarking on the docuseries Philly DA: Breaking the Law (BBC Four) was research its subject, Larry Krasner. Because there has to be a catch, right? An eight-hour film about a civil rights defence lawyer winning a landslide victory to become the first progressive district attorney in a notoriously conservative, corrupt city just doesn’t scan. A chronicle of him fighting ceaselessly for genuine change from within? No. Not in 2021. I’ve been here before. I want to be forearmed against the big reveal. So I searched. For the charges of fraud, revelations of – oh, I don’t know – historical sexual assault. That’s normally it, isn’t it? Maybe child abuse, to match the high – remember, it was not just a simple victory, but a landslide! – with the low. I put nothing past 2021, nothing at all.

But his record, as far as any awfulness is concerned, is like the Bellman’s map – a complete and perfect blank. Hard as it is to believe, Philly DA is a film about a good, not perfect man surrounding himself with good, not perfect people and trying to make a difference in a far from perfect world.

The film’s makers, Yoni Brook, Ted Passon and Nicole Salazar, follow Krasner from 2017, when he was elected to the position – the election field was opened up by the arrest and indictment of the then DA on 23 counts of bribery (he resigned and pleaded guilty to one of them) – until halfway through 2020. The additional challenges of Covid are not covered by the film, and it ends with the protests about the murder of George Floyd inserted presumably last minute, slightly awkwardly but understandably, under the credits. Almost certainly, they started from a pro-Krasner position and, human nature being what it is, more than two years embedded with him and his team had its effects. There is a warmth running throughout and, of course, their access remains entirely in Krasner’s gift and could have presumably been withdrawn at any time no matter how publicly his commitment to transparency had been proclaimed.

Nevertheless, Philly DA does not stray into hagiography. It is made clear Krasner is neither alone nor the Messiah, but was elected as part of a growing nationwide movement of people with progressive, reformist beliefs moving into prosecutorial positions they have tended to avoid (or been prevented from entering by the non-progressives already there). His inexperienced team’s missteps – notably losing control of the media narrative when they purge the office of the previous administration’s employees in what becomes known as “the Snow Day Massacre” – are on display. The problems caused by his unwillingness to smile, to gladhand just a little, to play retail politics and lubricate grinding wheels of the system where he can are noted.

In episode six, for example, during a particularly antagonistic period between the old and new guard and between public concerns and the DA office’s attitude to the establishment of safe injection sites for drug users, his ally Councilwoman Maria Quinon-Sanchez threatens to withdraw her support if he cannot find it in himself to give just a little (he does).

The trio of film-makers marshal a lot of material consistently well. Each instalment looks primarily at one subject, while continuing to tie it into the wider drive to change the policy of mass incarceration and break the harmful habits of career lifetimes among the remaining old guard. It fills in the city’s history while examining the result. It also looks at the effects of cash bail (which effectively criminalises people for being poor), the need for radical overhaul of a stunningly abstruse and uncompassionate juvenile system, the discovery of “damaged goods” files (secret records of police officers deemed too untrustworthy to testify in their own cases – wiped from employees’ computers but unearthed in hard copy in the archives).

There’s also the need for probation reform, the pressures of standing against the death penalty and the growing frustration among the activists who helped Krasner get elected and for whom, perhaps, no pace of change was ever going to be fast enough.

Transcending the directorial workmanship and production values, however, is the simple sight of unfashionable – which is to say good, ideologically informed but practically executed – work being done on behalf of the disfranchised, the powerless, the underserved. It is deeply thrilling to watch. An unfamiliar feeling stirs, and rises higher with each episode. The feeling is hope. “I don’t want to run for anything else,” says Krasner. “This is just an opportunity to do things that are really just about getting it right.” And remember, I checked ahead – you can enjoy it. Please do.