The Grand Union Canal links Birmingham to London with a waterway
which is 145 miles long and contains 166 locks. This cache is one
of a series to be found along or close to the
Hertfordshire/Buckinghamshire stretch of the canal.

This section of canal used to be dominated by vast paper mills,
which have now been cleared to make way for yuppie flats. The
diversion of the Grand Junction Canal at Apsley in 1818 from its
original route to follow the course of the Gade by Apsley and Nash
Mills which gave John Dickinson a local paper mill owner, direct
access to the canal network. All the Dickinson mills were connected
by canal to the Dickinson depot at Paddington (later Kings Cross).
From there deliveries were made to the London area.
The boats took finished goods to London and brought back raw
materials such as waste paper and rags. Other raw materials such as
esparto grass, woodpulp, chemicals and china clay were also used in
vast quantities. Once steam engines were in use in the mills, coal
came in by canal. During the period 1904-1928, the average annual
amount of coal delivered was 38,540 tons. The last deliveries of
coal were made between 1960 and 1970 as the mills switched to
oil.

The co-ordinates at the top of the page will get you to the
start point. Here you will find a the entrance to the new Apsley
Lock, canalside flats and marina development. Standing at the
Apsley lock sign over the roadway, you are flanked by the end of
two blocks. In total, how many round windows are there on the ends
combined? This number is A. That's it, this is the only
number you require, now for some light maths...
N51º 44.0(A/6)(A/4) W000º 27.(A/2)((A/3)+1)5
This place is muggle central, so you may like
to time your visit to the evening, or weekend. PLEASE if you think
you are being watched, leave the cache and return later.
Thanks.
The canny amongst you should be able to guess the cache location
without visiting the first location (especially in view of the
slight spoilers in the logs), but the cache was deliberately made
an offset to enable you to admire what they have done here!