Grass Snake or Adder?

[poppiesrara]

Not at all a great photo (shaky zoom), but can anyone identify this more certainly than my Googling has, please?:

On the Lizard in Cornwall a couple of weeks ago. Found in a sleeping spiral on the path before scurrying off down a hole, I'd guess about 16-20" long.

[Mal Grey]

A nice adder.

The sort of "zig zag" down its back is the obvious giveaway.

If you get close enough (!), they have slitted pupils in their eyes, whereas grass snakes have a round pupil.

[poppiesrara]

Thanks very much, Mal. I couldn't find a picture to match the markings properly (an adder with such light colouring outside the zigzag), but rather hoped he or she was that. I'll save the tender eye-to-eye moment for the next one I see, but at least I'll now know the key identifier!

[Mal Grey]

I love them, but haven't got close enough to eyeball one! Have with grass snakes, they're beautiful too.

The male adder is often quite pale, almost silver/grey sometimes, so likely a boy! Females browner and darker.

All this comes from the internet, as I've been reading up on UK snakes due to seeing so many grass snakes in the last year or so.