'Consumption Walls'

Consumption walls are so called because they are wide - this one is probably around 7ft to 8ft wide, and were made to use up (consume),

the smaller stones gathered from the field, when the process of enclosing land was first commenced.

They aren't too common, and this is the only one I've seen in the North Yorkshire Moors park.  

This specimen is at Danby Dale just south of Botton village at NZ 690031