The little rat - thought to be only two to three months old - was spotted scampering into the leopard's enclosure shortly after feeding time at the Santago Rare Leopard Project, in Hertfordshire.
So intent was the plucky rodent on its mission to snatch a tasty snack, that it seemed not to notice that its path was taking it within a whisker's breadth of 12-year-old Sheena.
Clutching a corner of raw meat with its tiny paws, the rat busily tucked in, until it sensed one of those whiskers moving in.
Sheena, bemused by the interloper coming between her and the remains of dinner, padded over on paws big enough to wreak vengeance with a single swipe.
But rather than giving the thief at very least the hearty set down it deserved, she gingerly lowered her nose for an exploratory sniff.
Rattus paused, lifted its dainty pink claws in submission, then - obviously deciding on a nothing-ventured-nothing-gained approach - continued to tuck in.
And after another tentative investigation, Sheena gave the leopard equivalent of a shrug and turned away.
...but even a gentle shove does not deter the little creature from getting his fill...
...so the mouse continued to eat the leopard's lunch and show the leopard who was boss