Richard O’Barry came to fame in the Sixties as the dolphin trainer for the popular Flipper series.

Ever since, he has fought to persuade us that capturing dolphins and forcing them to perform makes for cruel and dumb “entertainment”.

This story is only ancillary to Louie Psihoyos’s fine documentary, but it is indicative.

The central narrative of The Cove tells how O’Barry and his team infiltrated a lagoon near the Japanese town of Taiji, where local fishermen, having tempted the human-friendly dolphins there, slaughtered them to make “whale meat” for the locals.

Cast in the form of a thriller, the film unites free-divers and other activists in the plot to uncover the fishermen’s guilty secret.

Along the way, we see the Japanese government’s diplomatic wavering and the inadequacies of the International Whaling Commission.

The team, headed by O’Barry, plant thermal imaging cameras in fake rocks around the bay.

They watch as trainers from Sea World fly over the captured dolphins to pick out which ones to use for Flipper-like training before the slaughter begins.

Frankly, The Cove makes you despair but for people like O’Barry. “I was as ignorant as I could be for as long as I could be,” he says.

Not any more. But it clearly wasn’t easy to make so good a film out of his redemption.

One would imagine, and hope, that an Oscar nomination beckons.