I've seen these earthen banks marked on the OS map for a while, went and had a look yesterday -
SU3208 : Mystery earthwork on Row Hill, New Forest
Can't find any information on what its purpose was. Its not listed as being preshistoric (e.g. a long barrow) and doesn't look like that anyway. Its not an enclosure of any kind because the two banks are parallel and widely separated.
Any ideas?