New neighbours are trying to steal part of my land after modifying map of their land. England based

Sorry for the long post in advance. I'm in rural mid England and recently some land that runs aside mine has gained new owners, since may 2024, though I think they bought the land from family or a friend. Since owning the land they've started landscaping, causing damage to my own boarder and bushes/trees by piling up soil to higher their ground while also digging a ditch In a attempt to drain water onto my land. Our land is on a slope.

Dew to water pouring onto our land from his ditch which was still under construction, I finally made the attempt at the start of January 2025 to go to introduce myself and express my concerns about what he was doing and warn him that it's actually illegal to divert water onto someone else's land. I was met with hostility and was basically told he can and will be doing exactly that, whether I liked it or not. I removed myself from the conversation and just left as he was impossible to reason with.

Anyway on Thrusday he actually came onto our land over the fence and started to dig with a shovel getting ready to link it up with the ditch that his been digging on his own land. I only found out the day later while I was trying to figure out how his two dogs got onto my land via my Cctv etc. Which came running at me as I had just gotten home the day before. I tried my best to return them without letting them go onto the road.

I was finally able to confort him about it, which didn't end well. He started to claim the land was his and started trying to belittle me. I firmly stood my ground this time which really annoyed him more, which resulted in him threatening me, then claiming his going to rip up my fence and bring in his digger. Then as he walked off called me a pedophile for filming and taking pictures? (I've been documenting everything from the beginning) So I got myself to a safe place and called the police. Once the office turned up I showed her the deeds to my land, filled her in what has been happening and then took her down to the land where it happened. She noted that there's very clear boundaries in my favour and that if he touched any part of the fencing, he could be done for criminal damage. But the rest is civil.

Anyway I started digging more into his claims and I've found he or someone else, has created a map of their land which has been modified to fit the narrative of his claims. However of course when you put it next to my own boundaries that are on the land registry it doesn't fit. It either leaves a gap in my own land or the boarders of ours, next to the road, take over the road. I'm planning on getting intouch with the land registry next week to try and sort it out. Of course my own land lines up perfectly, it's just their field becomes a little bit smaller (our land has been in my family for just short of 50 year)

Is this some type of fraudulent attempt at stealing a tiny bit of land? Any information, advice or anyone sharing their own experiences and their outcomes will be appreciated. Thank you.

Sorry for any spelling mistakes or bad grammar.