The segments are expanded directly against the ground, which is London Clay.

The core typically extends 3 feet (90 cm) into the London Clay to form a watertight cut off.

The London Clay is well known for the fossils it contains.

London Clay has a stand-up time long enough to enable support to be installed without urgency.

London Clay is highly susceptible to volumetric changes depending upon its moisture content.

Below this is London Clay about 70 metres thick.

The western slopes, which lie on London Clay, support mature mixed woodland.

Its fossils were found in the London Clay, which was deposited around 50 million years ago.

These can also be found in the surrounding London Clay and were probably washed out to sea by large rivers.

The park slopes down into the valley, where the remains of old ponds lie on the London Clay.