Its structures, made of mud and coarse sand, are deteriorating due to increasingly extreme and fluctuating weather.

Add the butter and process until the mixture looks like coarse sand.

Heathland soils are made of coarse sand grains so are very freedraining.

Then spread some coarse sand (available from builders' merchants) over the ground and use a stiff brush to work it into the holes.

Lithologically, sediments consist of clay, silt and fine to coarse sand.