He’s nearly 100 years old and has spent more than half that time showing us the entire Earth, so it feels fair enough that David Attenborough has scaled back and stayed at home for this centenary year’s bundle of natural history wonders. There he is, in the sunshine in the middle of England, ambling past a shed. “Across the British Isles, there are magical places,” he says, whispering through the purple alliums. “Our gardens!”

Secret Garden’s conceit is to bring the super-high-res cameras and patient filming techniques that are usually deployed in the Amazon rainforest or the plains of the Serengeti and see what they can capture in British back yards. “Many of us are completely unaware of the wild world right under our noses,” adds Attenborough. “Some British gardens are almost as diverse as a tropical rainforest.”

Nearly all of them aren’t, of course. And although a future episode will look at foxes and hedgehogs in a small urban plot, much of the series is ensconced in the top 1% of British home patches, starting with an island on a river in Oxfordshire. The owners of the majestic mill house there, Sara and Henry, are surrounded on three sides by water and on the other by a fabulous garden, two-thirds of which they allow to run wild due to regular flooding.

The house and its grounds bring us a gorgeous fantasy of beautiful old England, teeming with cuteness. Yet despite the animals concerned being familiar old friends, the programme tells the sort of thrilling stories of predation and survival, mating and nesting, that we’re used to when Attenborough is in Africa or Asia. There is, indeed, a whole world between those grassy banks.

“One of the most exciting things that happens here,” Henry enthuses, “is that you get this flash of blue followed by a whistle – and then there goes a kingfisher!” Secret Garden catches much more than a flash, showing us the bird waiting on a tree branch, then swooping to the water. A special effect demonstrates the difference between what a human can make out when they gaze at the reflective surface of the river and the much clearer picture seen by the kingfisher, which has special oils in its eyes that tone down the glare.

The kingfisher finds a mate and, in a terrific shot of the pair in flight, Sara is in the background, dutifully mowing a lawn. She and Henry keep reappearing as supporting characters in the story, emphasising how close to modern life the wildlife is. When Sara tosses a handful of nuts and seeds into her bird feeder, the few that spill on to the lawn below create a perilous temptation for a little bank vole, coming out of hiding to dodge through grass that might just be home to a grass snake.

The most fearsome predator in this ecosystem, Oxfordshire’s answer to the lion or crocodile, is the otter. It lives in the vacant space below the room where Sara and Henry watch telly and it wants to eat their friend Doris. Doris is a mallard.

The competition between male mallards to mate with Doris leads to a fine display of quacking and splashing in the river, filmed with Henry blithely hosing herbaceous borders in the middle distance. Henry’s and Doris’s activities continue to run in parallel as she nurtures nine chicks in a willow-tree hollow (Henry potters with a rake and barrow), flaps down from the tree to the ground with the flightless newborns forced to take a terrifying leap behind her (Henry primps a shrub with long-handled loppers) and streaks across the lawn with her children in a waddling pack, struggling to keep up (Henry sits inside with a coffee and the Financial Times – rather magnificently, this scene is filmed from inside the house, over his shoulder).

Henry is absent when the otter appears just as Doris is swimming across the river with her vulnerable chicks, but she doesn’t need his help: her ingenious way of escaping without any of her kids being eaten is a lot less fuss than most scenes of parents protecting their young in nature documentaries, but no less impressive for that.

When summer bank holiday sunshine prompts a mayfly nymph to leave its river berth, shed its skin twice and risk being eaten by a damsel fly so it can join the other mayflies dancing on dry land, the haymaker shot captured by Secret Garden’s cameras is almost too perfect. Hundreds of mayflies, wings glinting, flutter in the buttery light against a backdrop of bunting and Victoria sponges, because today is the day Sara and Henry have thrown a lovely garden party for their friends. We’ve stayed at home, but we’ve truly escaped.