The cache is not at the headline coordinates. This is an Adventure Lab Bonus Cache. You will need to complete the Adventure Lab, Samuel Pepys' Buried Treasure https://adventurelab.page.link/FEXa first. Use the Adventure Lab app to download the Adventure using the link, or scan the QR Code below:
*** PLEASE NOTE - the Ad Lab is sequential because it tells a story. We are lucky enough to have a lot of caches in the area, you will pass a few on the way round so due to proximity rules the bonus may require retracing your steps ***
Each point of the Adventure Lab visited will give you an important number to use to calculate the final co-ordinates to discover the missing hoard.
Calculate your route to the final using the following;
N 52 19.A (B+C+D) (D-E) W000 12.(B+C+E) A (A+B+D)
Good Luck.