Perhaps we are being too dismissive. Sheep may be turning nasty.
One made a grab for my cheese sandwiches on top of Kinder Scout a few years ago. I had to give it a shove with my boot to make it move away. It took a real push too, its grip on the ground was remarkable.
..... and I bet it wasn't the first time, for what on earth was this supposedly grass-eating brute doing lurking on a completely vegetation free patch of peat and rock? Plotting to attack walkers and steal food, I'm sure.