Harbourneford Clapper Bridge
It's been here a while as it was listed in the Domesday book. Other people have mentioned a more recent book by John Hayward called 'Dartmoor 365'. It divides the moor into it's 1-mile square and seemed like a good photographic tool when looking for ideas for somewhere to go. There was a sketch by the author of this fine old bridge so I went to take a look. The author states that metal handrails are fitted, probably as an 19th century health and safety measure and he took the libery of not including them in his sketch. I considered what's good for the goose is good for the digital gander so I've photoshopped them out with a bit of Content Aware Fill.
There are a couple more here with different views.