The published co-ordinates are for a ventilation shaft on the Watford North Rail Tunnel, part of the 112 mile (180km) London to Birmingham railway line opened in 1838 when it became the first intercity line to be built into London. Not obviously relevant to the puzzle, it is an interesting landmark nonetheless and the suggested parking for the finals would also be convenient to walk to here. There is a similar shaft close by; can you spot it? The cache is hidden less than 1km away; to find out where:
Identify the link of the seven pictures then find out how they work for the decode into the formulae:
N51° 4(D-C).(E-F)(A-B)(E-D+G) W000° 2B.(C-G)(F-B+A)(E-D)
Parking at GZ is NOT recommended. Suggested parking on unrestricted road can be found in additional waypoints.
Cache contains log only; please bring own pen.
*****Count the number on the cache for a future bonus*****
