Over thirty years ago my wife and I were out for a stroll near our home and were returning along the roadside footpath that led towards our house. Stood in the road was a policeman who looked rather concerned and apprehensive; he was staring intently at the ground. As we approached we could see he was looking at a snake in the middle of the road! He obviously wanted to move it but was not at all sure whether he would survive the experience. I was pleased to be able to tell him it was not an adder, it was a grass snake. "Err, how can you be sure?" he asked. No V on the back of the head, no zigzag design down the back, yellow patches on the side of the head, too large to be an adder, wrong habitat - he was convinced, picked up the snake and moved it to safety at the side of the road!
Although called the grass snake (Natrix natrix) this is not a snake that we often see in grassy areas, not because they are not there but because they are hidden. They are also nervous creatures that will generally slide away as soon as they detect you approaching. You most frequently see them in water, they are strong swimmers. They can be seen in lakes and ponds, including garden ponds, where they are both looking for food (they adore a fresh frog for lunch) or they are cooling off on hot days. They have become increasingly uncommon in the wild and large gardens with a pond and a good compost heap are now their preferred habitat where they stalk their prey and eat it alive which can be disconcerting if you hear the screams of a frog that is half inside a grass snake!
Going back to the opening story, I have since found out that they often 'play dead' when under threat which is probably why it was lying in the road when approached by the policeman, there being no cover to 'run' to. I also understand that they can release a foul smelling liquid from their anal gland when handled and stressed so I reckon that policeman got away lightly don't you?