Ken Loach built his career on films of protest, depicting the oppressed of many places and many eras in their struggle against their oppressors.

The Brit’s “socialist realism” was obvious from his breakthrough English working class classic “Kes,” with the Irish Republican thriller “The Wind that Shakes the Barley” and the Spanish Civil War” drama “Land and Freedom” among the career highlights as he’s bounced from socially aware documentaries (“McLibel”) to working class exposes (“I, Daniel Blake” and “Sorry We Missed You”) and comedies (“Jimmy’s Hall”).

Loach announced his retirement a couple of years back. But that just gives his fans and cineastes a chance to finally catch up on all the good films he made that we’ve missed.

“Black Jack” seems, on first glance, a little out of character. A Dickensian drama of the “Great Expectations” school, it’s set pre-Dickens, a sharply-observed thriller of working class trials and tests of the pre-Industrial Revolution child labor era — 1750.

It’s modest and downright primitive, with period-correct Cockney that almost requires subtitles, and yet it’s a beautifully realized period piece, a reminder that somebody had to be serving, waiting on and driving the carriages of all those Jane Austen heroines and their landed swells suitors.

The carriages and stagecoaches get muddy, the predatory rich are preyed upon by the just-as-clever predatory poor and the entire picture, with its “unimproved” roads, rough trade and roughly-clothed characters, feels lived-in and thanks to the spring shooting schedule, dewy and verdant.

And the more the story unfolds, the more this adaptation of a Leon Garfield novel resembles “Great Expectations.”

Jean Franval plays the title character, a Frenchman named “Black Jack” “because nobody could pronounce his real name.”

We meet him as he’s prepped for the gallows, a murderer about to meet justice. But we don’t get to know him until his body is delivered to the business of Mrs. Gorgandy (Pat Wallis), a widow who makes her living providing corpses for scientific-minded surgeons.

A draper’s apprentice, Bartholomew (Stephen Hirst) is charged with “watching over” the corpse while Mrs. Gorgandy goes out to complete the sale, so the boy of about 12 is the first to realize Black Jack has ingeniously cheated the hangman.

The kid is kidnapped, forced to help the hulking Black Jack flee the city and escape to the country. Young “Tolly” may not be the thug’s conscience. But he finds ways to thwart Jack’s criminal intent, collecting cash for helping push a coach out of the mud when Jack’s first instinct was to clobber and rob the passengers and coachmen.

Their picaresque odyssey takes a turn when Jack contrives a way to ensnare a second coach. A twelve year old girl (Louise Cooper) escapes her trip to a “retreat” (“the madhouse”) and Jack is offered money to track her down. That means the job falls to Tolly.

Tolly finds the girl Belle, and realizes that she might be “savable,” as she’s being shipped off to hide a wealthy family’s “shame” over her (non-hereditary) illness so that her older sister can marry a lord. Tolly becomes her protector as he and Belle tumble into a traveling fair and its “miracle elixir of youth” “doctor” (Packie Byrne) and join their ranks.

But Black Jack still wants the reward for the girl. And a fellow hustler with the fair, Hatch (Andrew Bennett), sees pounds and guineas in the lass and whoever might be looking for her.

The snake-oil pitches to the gullible are one source of chuckles in this dark yet often sentimental “comedy.” But young Hatch’s audacity is Artful Dodging at its best — blackmailing the shady “madhouse” doctor (Russell Waters) who “lost” the mentally disturbed girl from a well-off family, and then blackmailing the child’s father (William Moore) about the family “secret.”

The youngest players have a whiff of “amateur” in their performances. But the supporting cast isn’t entirely made up of unknowns or little knowns. Waters and a few others were veteran character players. And the fair’s troupe of little people dancers — Mike Edminds, Malcolm Dixon and David Rappaport — would soon achieve screen immortality for their hilarious turns in Terry Gilliam’s “Time Bandits.”

Loach’s early career was filled with modestly-budgeted films that punched above their weight, and “Black Jack” is an exemplar of that. It may not be the most original picture on his resume, as that source novel leans a tad too heavily on Dickens to surprise us.

But it’s a lovely immersion in how the other three quarters of Britain lived in the days when “The Empire Silhouette” was what the well-dressed Austen contemporaries aspired to and “poor” wasn’t just a term reserved for English roses with no dowry and limited “prospects.

Rating: R, violence

Cast: Stephen Hirst, Jean Franval, Louise Cooper, Packie Byrne, Joyce Smith, Russell Wallace, William Moore, Pat Wallis, Mike Edmunds, Malcolm Dixon and David Rappaport.

Credits: Scripted and directed by Ken Loach, based on a novel by Leon Garfield. A Kestral Films/Cohen Media group release streaming on Tubi, et. al

Running time: 1:44