The 97-year-old food writer Diana Kennedy is the very model of something rarely seen today, or even 20 or 30 years ago: the formidable Englishwoman abroad. And, despite having made Mexico her home for decades, and being deeply respected there for her lifelong mission to educate the world about Mexican cuisine, I suspect she still thinks of it, just a little bit, as “abroad”.

This short, sharp, marvellously watchable docu-portrait of Kennedy shows us her life in Michoacán in western Mexico, vigorously engaged with her community, lecturing and giving media interviews and masterclasses in Mexican cooking, taking long walks, driving herself around the place, visiting markets and not hesitating to tell stallholders if their produce isn’t up to scratch.

Film-maker Elizabeth Carroll tells us about Kennedy’s eventful, romantic early life. Born Diana Southwood, she was a traveller who met and fell in love with the New York Times’s Mexico correspondent, Paul Kennedy; living with him in Mexico City, she conceived a great love for Mexican food. After his death and with the crucial encouragement of the paper’s food correspondent, Craig Claiborne, she began to publish the wondrous recipes she had uncovered on her travels all over the country, and introduced the world to Mexican cooking the way Elizabeth David introduced everyone to French cuisine a generation or two before.

She is now a passionate stickler for getting Mexican food right – which means doing it the way she says, and who on earth is going to contradict her? Even the timid souls who merely ask (reasonable) questions in her class can get told off a bit. I would have loved to hear Kennedy on the tricky subjects of fusion cuisine or cultural appropriation. But there’s more than enough here to get your teeth into.

• Diana Kennedy: Nothing Fancy is available on digital platforms from 1 May.