If you have found all 5 lab caches to complete my Adventure, 'Green Spaces of Hatfield Peverel', then you should have gathered all the clues needed to find this physical bonus cache. You can go back into the journal to view these again, but here they are for reference:
1. Strutt Memorial Ground: Number of letters in the answer = A
2. The Green: Third digit of the answer = B
3. St.Andrew's Church: Number of letters in the answer = C
4. Hatfield Peverel Cricket Club: Answer to the question = D
5. The Duck Pond: Number of letters in the first word of the answer = E
The cache can be found at: N 51 46.(A-D) E A E 000 36.(A-C) E B
Fittingly, the partially green cache is in another small green space, hidden by some greenery.