A series of puzzle caches each involving substitution ciphers. Once all the puzzles have been solved you should find that you have a circular walk of about 4 mile, mostly along footpaths and fen roads, there is a short stretch along a busier road but there is a good footpath. There are a couple of styles, and at the time of placing there was no livestock.
You may spot some flowers along the way, but beware of the roses for the thorns may make you cross.