The Parnholt series on an off-road loop (walk or ride) of just over 7 miles through some fabulous Hampshire countryside (see 1. Parnholt (GC3PXNE)for full details of the series). To find the bonus cache at the end, you need to collect the numbers allocated to letters in some of the cache logbooks on the Parnholt loop (1. to 19.) - not all caches have bonus clues. BYO pen.
Here is a suggested route, which shows other caches you can bag on the way round:
Then do Parnholt loop 1 to 4
Then backtrack for Parnholt 5 to 13
On the way to Parnholt 14 you can do Chilihouse's Battle of Britain (GC23Q3X)
Then it's Parnholt 14 to 17
Please replace all caches as found and log any interesting aspects/photos of your walk round.