Friend has a stream at the end of the garden. Boundary is on the line of the stream, so their understanding is that means down the middle i.e. neighbour owns bank on their side & friend owns bank of her side.
Friend has no fence between garden & river, neighbours have a fence on their side. It's been like this for years.
The neighbour has a gate in the fence, all fine as he can access his side of the stream, the problem is he keeps coming through and crossing the stream and cutting my friends plants bank (which aren't overhanging the stream and don't need cutting back) and throwing the debris in my friends garden. He's also physically taken rocks (large decorative ones bought from a garden centre) from my friends riverbank because 'he didn't want them there'. When he's told not to trespass onto the other side of the stream he goes completely nuts, shouting and screaming that he's doing her a favour etc. Horrible man, very aggressive and doesn't listen when he's told he can do what he likes his side, but not to cross the stream.
It's really not great as he is essentially opening a gate onto my friends garden - it's not a big fancy house, just a normal 3 bed property with the stream 20 metres from the house. I'm a bit concerned for her security and also that he seems unreasonable to say the least so I wouldn't trust him to do further damage.
Is there anything my friend can do, or does she just have to put up with this idiot and his actions?!