Martin Le-May was out for a stroll with his wife Ann in east London's Hornchurch Country Park on Monday when he stumbled on an incredible sight.
Le-May, a photographer, hoped to spot a green woodpecker, he told The Huffington Post UK.
But he found plenty more. The couple saw a woodpecker struggling on the ground before it flew past them with a small animal on its back.
It turned out the woodpecker was set upon by a weasel and was fighting for its life.
Le-May snapped an outstanding photo that had been re-tweeted almost 9,000 times as of Tuesday afternoon, after someone else posted it on social media.
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The bird eventually doffed its attacker and flew away, while the weasel "just disappeared into the long grass, hungry," Le-May told HuffPost UK.
Lucy Cooke, a wildlife expert, told BBC News that weasels don't normally prey on woodpeckers, but that they are "fearless" animals.
"A female weasel weighs less than a Mars bar but is as ferocious as a lion, so this is why the woodpecker would have been able to take off with it on its back," she told the network.
The photo has become a meme, #Weaselpecker, and spawned plenty of alterations on social media.
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