This cache is in a small key safe that is easily found near the old RAF Holmpton, or as it is called locally "The Bunker".
As we are at the site of a military facility that was very much involved with signals, (and therefore codes and ciphers), it seems appropriate that access to the log should only be obtained by decoding a cipher that hides the required number. So good luck with this simple but multi step process.
Step 1
You need to start with a four letter word that is most commonly used to describe the war that the Bunker was designed to contribute to.
Step 2
Take that four letter word and convert the four letters in it into numbers using a simple shift cipher. An example of such a cipher is A= 1, B=2, C=3 etc, but it’s not that one. You will need to work out what transformation you should use from the information you have been given (or you could try trial and error or guessing it, but that may take some time).
Step 3
You should now have 4 numbers, some or all of which have 2 digits, for example 16, 20, 9, 13. You now need to convert these into 4 single digit numbers by adding the two digits together in each case. The numbers above would therefore convert to 7 (1+6), 2 (2+0),9, 4 (1+3).
Step 4
Insert the 4 digits (7,2,9 and 4 in the example) into the key safe and sign the log!
(I have marked this as "special tools" required solely because I would struggle to do it without pen and paper, but you may be more capable than me.)