My question involves real estate located in the State of: Texas

Own lot (Home) purchased in 1989. At time of purchase lot behind and adjacent to my lot was undeveloped with about a 30 degree slope. About two years later returned from a trip and the lot owner(a builder) had decided to build on the vacant lot. The builder hired a landscape contractor to erect a retainer wall "on the lot line" and the wall was built and the builder back filled the lot and began working on foundation. the retainer was erected and filled while I was not here, so I didn't authorize anything and nothing was discussed with by the builder or individual who built the wall.

Time passed and the house sold about three times and by 2008, there was a third owner. By the third owner, the retaining wall that is retaining the fill on which his home and swimming pool is built was in a sorid shape. No maintenance, removal of undergrowth or anything was done by neighbor. This is a platted subdivision with all lots surveyed and on file with the County. I talked to the third owner several times over the next few years about his plans to either repair or replace the failing retainer wall for his property. His steadfast answer was, "it is not my wall; it is your wall, and it is on your property."

I had no idea where the lot corner lines of my lot were since they had been covered with dirt years before where they remained for many years. The retaining wall, built more than a year after I bought this home and lot, does not show the retaining wall on the original survey, because it was not there. The neighbor on the other side of the lot in question also had a retainer wall issue which he had been talking to the owner for some time as well. The retainer wall owner also told the neighbor the same thing, "that is your retainer wall; not mine, and it is on your property." Upon return from a trip recently, there is a contractor (the same one who originally built the retainer wall in question) working on the retaining wall between the neighbor and the one in question. The new retainer wall intersected the retaining wall on the back of my lot and from the original corner pin, it seemed clear the entire retaining wall was built on my property. I hired a surveyor to survey my lot and found that the neighbor's entire retainer wall, built in about 1991 or 1992 is on my property, so the neighbor was right, his retainer wall is on my lot. After talking to the original owner of the undeveloped lot, he said that he hired this landscape contractor to erect the retainer wall on the property line, but it seems the landscape contractor erected the wall on my side of the property line rather than the correct side, the side the natural state was "disturbed".

My position, based on my neighbor's position being that the wall is my wall, not his, and it is in fact on my property, then since it was erected to retain fill dirt that altered the original lay of the land, that the wall is encroaching on my property and I should be able to have it removed, and let him worry about building a new retainer wall on his property where it belongs.

However, a real estate attorney I spoke with today said, that since the encroachment occurred more than 10 years ago, and I discovered it a week ago, that Texas law says he had the right to my property through " Adverse Possession on which the builder who build his home encroached on my property. He also says that even though the neighbor claims it is not his wall and it is my property that I can't remove the wall. It is my understanding that "Lateral Support" is the right to have soil in its natural state be supported by the land adjoining it, and that No absolute right of lateral support for land existing where the natural condition has been altered through man's activities so as to create a need for lateral support whre note previously existed in nature.

So, who is responsible for building a retaining wall to retain soil altered by man on my property without my knowledge or consent?