The headline co ordinates take you to a sign placed by Bridport Town Council from which the following formula will give you the Northings
Use first five digits on bottom row =
A B C D E
.
Then move to waypoint 1 and find plaque to solve the following for the Westings
Fourth row : third digit of year = F
Fifth row: first digit = G
First row : fourth digit = H
CHECKSUM : A B C D E F G H = 31
The cache can be found :
N 50 43. (B + E ) D (C+C)
W002 45. F G H