I can trump you all - our neighbours deliberately built their extension across the boundary to try and take some of our garden. They gave us fake plans and supplied fake plans to Southwark (who did little when they discovered this), both surveyors (party wall surveyors). Their own builders ran away from the job and have refused to meet my surveyor. When I said I would pay for a boundary surveyor to try and resolve the issue, the owners refused. I arranged for mediation and they shut that down. Our security cameras which we had to buy due to the behaviour of the builders, were hacked. Our property was watched as the builders were waiting for us to leave in order that they could move the fence further in to our garden. My husband was followed the street and intimating heavies were behaving in a threatening behaviour and we had chalk marks left on our wall. If you think I am making this up please DM me as you are welcome to see the extension, fake plans, hacking footage etc.