This cache was recently muggled. Please use stealth when retrieving and replacing!
This is one of a series of large black nano caches (about 3cm wide) aimed at children aged 8 in a somewhat cache-bare area. The caches are intended to be relatively easy to spot, though a certain amount of stealth is required! The cache images section has a photo of the kind of cache you're looking for.
Four of the five are on the main part of the common, and the last cache will require you to cross Rookery Road (which has a pedestrian crossing but is still a busy main road). All of the caches can be accessed from on the grass of the common without the need to cross any other roads.
Please don’t send children to retrieve these caches unsupervised. In any event, one of the caches will likely require the help of an adult to retrieve it from its hiding place.
Good luck, and happy hunting!