1.   In the last one million years the ice sheets spread a layer of boulder clay across the lowlands.

2.   The calcareous clays, such as East Anglian boulder clay, are alkaline and therefore will not suit azaleas or rhododendrons.

3.   Their floors are covered by sheets of boulder clay.

4.   When the ice melted some shallow lakes remained where boulder clay blocked old river courses.

5.   Where it was melting a huge pile of boulder clay was built up, as a terminal moraine.