We hv a side garden which is 22 metres long by 8 metres wide n about 1.2metres higher than the house. As it is an area with tree protection order, I was told we cannot build a brick retaining wall. I was given the suggestion of a sleeper retaining wall but I don't like that visual effect. Is there any other alternatives which wl allow me to abide the TPO n yet hv a better visual presentation.