Apologies in advance for any frustrations and I hope your holiday isn't spoiled by carrying round a wad of photos. It's meant to be hard, perhaps requiring more than one year for regular visitors. To keep things fair, for this cache, I won't be replying to hint requests; at least for a year (Although if you can tell me the item but think the instruction for generating a number is ambiguous then do email as that's not meant to be puzzling.) I'm not sure quite how hard it is so log notes on the number of items found would be welcomed (no spoilers please) and I might up the difficulty to 5 if all is quiet.
Where appropriate, convert letters to numbers according to a=1, b=2, ..., z=26.
The cache is at N 49° 5S.TUV W 006° 1W.XYZ
A-B=S, C-D=T, E-F=U, G-H=V, I-J=W, K-L=X, M-N=Y, P-Q=Z.
Image 1: A= The final erased digit
Image 2: B=The 3rd digit on the small plaque below the item
Image 3: C=The first two digits of the PATENT No.
Image 4: Look nearby for a date stone (2 numbers, 2 letters, 2 numbers) just to the right of the steps that would be the entrance. D: The final number, on the right of the stone, is clearer than the rest. Add 3 to this number to get D.
Image 5: E=The first letter on the plaque detailing when it was opened.
Image 6: F=The 1st digit of the number on the side of the item
Image 7: G=Sunnyside (The ladybird has gone)
Image 8: Look for the nearby information board. The item "was begun in ***H. But, ..."
Image 9: I=The 3rd letter of the second word plus the 1st letter of the third word
Image 10: Find this cannon. There is a large, white, single digit at a height of around 2m within 5-10m of the cannon, That is J. (Note that this is the original clue. The digit was removed but has now been replaced.)
Image 11: December 2018: Temporary question. Behind this object is a device with two main components. In the bottom left area of each component, the same two letters, one on top of the other, are very clearly marked. What are they? K= : YY=1, ZZ=2, YZ=3, ZY=4, XX=5, XY=6, BB=7, AA=8, AB=9.
Image 12: Find the number immediately following "TR21". L=its 1st digit.
Image 13: This dog seems to have disappeared although it may be lurking somewhere. It has at least two similar siblings which will tell you that you are in the correct general location. Then look for a historical information board about flower exports: "... to Covent Garden in *M*0. The ..."
Image 14: N= Subtract one from the similar looking number nearby. Note that in August 2018 the path that comes very close was less clear than in the past.
Image 15: Look for this unusual headstone. Nearby, ELIZABETH, DAUGHTER OF HUGH & JANE died aged P
Image 16: Within a few metres, Joan was born on the Q th day of March
One member or other of my extended family will be lucky enough to be staying near the cache for more than half of the year and will keep an eye on it. Sorry, I didn't have a FTF prize but if it's unfound when we next visit I'll drop one off.