From the lone tree...

On Dartmoor there are around 3,000 'letterboxes' - small, usually plastic waterproof (ish) containers with a rubber stamp and a notebook inside. When you find one, you stamp your own notebook as proof that you've found it, and write something in the notebook from the box - usually a comment on the weather, and how many other boxes you've found that day.

They are hidden all over the moor and, a couple of times a year, you can go to a particular pub in a particular town and get a copy of the latest list, with clues to their whereabouts (it's a bit like geocaching, but without a GPS, and with a map and compass).

Many of the clues go something like this:
"From lone tree on...side of tor, walk...paces on a bearing of...to large flat rock that resembles a... Box is found in small hole under rock"

You'd be amazed how many lone trees and flat rocks there are on Dartmoor!