The Common
Cannon Hill Common consists of 21 hectares (52 acres) of land that was once part of extensive holdings belonging to Merton Priory, and was farmed for centuries. Thomas Becket was educated in the priory in 1130, and Nicholas Breakspeare was a monk at the priory in 1125 ,who later became Adrian IV, the first English Pope, in 1154.
The estate was first sold off in 1613, and the land was occupied by Parliamentarian forces during the English Civil War. (A row of cottages named "Cromwell Villas" once existed on Cannon Hill Lane.)
Cannon Hill House was built some time in the 1770s by William Taylor, a Major General in the 14th Regiment.
The house changed hands several times until being purchased by Richard Thornton, a Baltic trader, in 1832, who lived in the house until his death in 1865. The house was barely used over the following years, falling more and more into neglect until finally being abandoned in 1880.
Maps produced into the 1930s still show the house, although it was most likely already demolished by 1900.
The land was eventually purchased by George Blay, a local developer (who built most of the houses in the estate(s) surrounding the park), who offered 60 acres of land to Merton Council, who eventually purchased 53.5 acres for £17,610. The park was officially opened in 1927, and the site of the old mansion itself was fenced off and declared a bird sanctuary in 1929
The common was designated a Local Nature Reserve in 1998, and today boasts 2 meadows, and mature woodland with some trees as old as 200 years.
Friends of Cannon Hill Common website
Cannon Hill Common on Wikipedia
The Series
This is a small cache series centered around Cannon Hill Common and some of the surrounding recreational land.
Each hide/container is different from each other, and each container has been crafted/chosen to blend in. Please don't give up if you don't find a plain 35mm film canister in "base of tree" 
The Cache
This cache is not at the posted co-ordinates. At the co-ordinates you will find an information panel on Cannon Hill House. The year the watercolour was painted = ABCD.
The cache is hidden at co-ordinates: N51° 23.[A+B][B-A][C], W000° 13.[A][D][D+A]
The checksum of all digits in the final co-ordinates is 45.
Please do not post spoilers. Thanks 
Logs containing spoilers and/or spoiler photos will be deleted.