Neighbour changed guttering pipe (without consent), now the guttering is overflowing

[Youngoldguy]

So pretty much the title;

I went on holiday last year July and then a week after I came back I noticed that the front drainage piper which comes from my gutter had been cut and redirected to a new pipe above my neighbours front porch.

The Guttering runs across four houses two to my left and then my neighbour on my right with me in the middle.

When I asked him he said he was getting flooding in his porch, however that couldn't be possible as there was no pipes going into his porch, as they go directly into mine (actually in my porch-extension then into the ground).

Now when it rains hard the water flows back and pours over the edge across my main window bay, causing serious damp on in my main bedroom and running on my front house bay.
The replacement connection he has had is slightly too high which I am assuming is the problem by not being angled low enough.

1) He trespassed
2) He changed the pipe work without permission of the houses affected
3) It is now causing damage

Am I wrong in thinking this is pretty straight forward that he needs to fix this?

[MIKE770]

have you spoke to them?

[Youngoldguy]

have you spoke to them?

Yeah, he said "it isn't his fault because the overflow was damaging his property and it needed to be corrected, and that mine is due to the guttering needing to be replaced". Even thought the problem only occurred after he changed the down-flow pipe.