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We've seen lions hunting giraffes, watched cheetahs chase down gazelles, thrilled at wolves hunting caribou and gasped as crocodiles snatch baby elephants.

But in all the remarkable wildlife footage presented by David Attenborough throughout his long lifetime, there's little more jaw-dropping than the sight of an otter hunting ducklings in an English country garden.

Secret Garden is shot entirely in the UK, yet the dramas it captures are worthy of the Serengeti or the Amazon rainforest.

In fact, Sir David informed us: 'Some British gardens are almost as diverse as a tropical rainforest.' 

For the opening episode in a five-part series of lyrical beauty, he took us to a mill house in Oxfordshire, hemmed on both sides by a river, with kingfishers, deer, herons and five species of bat.

The apex predators were the otters — though owners Sarah and Henry have lived in the island house for 30 years and seen the animals only two or three times.

At first, the camera team was afraid they wouldn't catch even one glimpse. It wasn't for want of trying: cinematographer Sam Oakes set up his hide in the middle of the river, sitting waist-deep in water for hours on end.

But it was his colleague Matt Tomlinson who struck lucky, as a female mallard nicknamed Doris led her chicks across the water.

 A ripple appeared by the far bank, the sort of swell that might indicate the presence of a monster in Loch Ness. Then a savage little head popped up.

The shot was perfectly composed, with the vulnerable ducklings a blur in the foreground and the hungry otter in focus beyond them. A kill seemed inevitable.

But the ducklings weren't defenceless. Brave Doris paddled towards the otter, a living decoy duck, pretending she hadn't seen the danger till the hunter lunged. Then she took off like Roadrunner, leaving Wily Coyotter in her wake.

Henry and Sarah love their resident kingfishers so much, they even have one on the sundial above their door. But this will have been their first peep inside the bird's burrow, thanks to a tiny camera buried in the riverbank.

I've certainly never seen kingfisher chicks before, and was fascinated to learn they are skinny, pink and featherless, like human fingers, when they hatch. Another nest-cam showed us baby bank voles — 'smaller than a jelly baby,' remarked Sir David, with his typical mastery of the memorable phrase. 

Attenborough devotees, and I'm proud to be one, will remember the breathtaking opening of his 2014 series Life Story, in which barnacle goose chicks threw themselves down a sheer cliff.

It turns out that mallard chicks, hatched in the fork of a tree, have to do much the same thing... though they fall only a couple of feet. English gardens can be as wild as anywhere in the world. It's all just on a smaller scale.