This is a bonus cache for the Adventure Lab series of caches along the Phoenix Trail.
The cache is not at this location. To solve it you will need to complete the Lab caches and note a bonus number at each.
You are now at the Shiplap Shelter by Rory Lobban. One of the sculptures on the Art Trail which runs over a distance of 5 miles between Thame and Princes Risborough along the Phoenix Trail.
For the bonus cache you will need to note how far it is from Henton to Ilmer, this is “f”.
Assume 51 43.XXX N 000 51.XXX W
The cache is at
N. a (b+1) (b-c) W. d f (a+e)