Neighbour diverted their downpipe onto our extension

[weq4]

Hi,
the neighbour has built extension next to ours and I noticed that the downpipe from gutter has been cut short and diverted so it pours out onto on our flat roof extension.
What do people advise I can do, please?

Talk to them? Take some photos too.

I would talk to them but very much blame the builders and give them a chance to claim they knew nothing about it. Then tell them to get their builders to rectify it.

If you don't want confrontation ring the council planning first. Your cf ndn may have intended this to happen.. Builders may think you agreed to it.

Speak to them first obviously, they may not know.