About 4" above the ground. Plaster sucks moisture up from the ground, the walls were damp about 18"-2' high off the ground. Rising /structural damp (not the TV sitcom either).
The house I am working on in Lancing had a leak below the stopcock last week and ruining my lovely newly plastered walls. The water meter isolator in the street wouldn't turn off the water to the house. Called Southern Water, they answered in 2-3 mins max. Then had a surveyor phone me an hour...