Trespassing

[PROBABLE]

My neighbourssolicitor wrote to me saying that my neighbour had an oral agreement with the then (the one before the previous one) owner of the property to put a fence inside the (mine now) land, No proof is given. Can I take this strip of my land back by writing a letter saying "I revoke that oral agreement..."

[efpom]

Is there a scrap of documentary evidence that such an agreement existed?

[PROBABLE]

None whatsoever. The neighbourbought the property in Oct 1997. Somebodyelse was the owner of our property at that time. Our property was sold in 2000 to an old couple , the man died after about 3 years the lady developed Alzheimers and later on cancer and died in 2012. We bought the property in March 2013. In June 2013 we (me and my wife) challenged the owners about the trespassing overhanging roof gutter and the strip of land at the front garden. His reaction was "I had permission from the previous owner" After three days he knocked on our door to say, "you surprised me the other day , and I told you I had permission, in fact I found them like that" We had three meeting in July 2017 to discuss how to sort out the trespassing issue. We reached no agreement . Himself telling us "I found them like that". We engaged solicitors in December 2018 trying to resolve the issue by somekind of agreement. He has refused repeatedly to jointly appoint a surveyor/expert to determine the boundary line and be binded by his findings. His only defence is "I found it like that". His last solicitors letter stating that they have adverse possession for the lans at the front and easement by description for the guter (due to long use, meaning over 20 years). Again no evedence have been given to us apart from "They have been there" since they bought the land .
Adverse possession he cannot claim because the strip of land had not been fenced, I entered it without hindrancain his presence once a year to trim my small trees, and during Decem 2017 up to July 2018 when I had major works done in my house , both myself and the workers used to walk over this land every day because my fron entrance had been closed with metal sheets for security and only opened for vehicles to enter the forecourt . We were never challenged. Thank you.