Flooding in Garden from NDN

[Mistoffelees]

I wasn't sure where to post this but hoping it gets some views here.
A few months ago we noticed there was a slightly squishy patch on our lawn near the boundary with the NDN, spoke to them and they said it was probably their pond and duly relined it. I gave it a chance to dry out but if anything it's got worse. We've trimmed the hedge near where I think the problem is right back and behind that is a low wall on which we can see water constantly. I've mentioned it again to our NDN who has just said "Oh that's strange because we've relined the pond"
What can I do now? I've tried googling but advice I can find is for if the water is from flooding that has now stopped or "helpful" suggestions to dig a pond

Do they have a drain near that area? If their drain is blocked water may have found a way out.
In these drought conditions it’s unlikey to be a high water table.

I'm not sure, I can't see into their back garden from our house. I would ask the NDN but from how she responded to me saying our garden was still boggy she seems to have washed her hands of the issue.

Is it their wall? Presumably the pond wall. Can you paint it with water seal type paint?

No it's not the pond wall, the pond is a few foot away from the wall, I'll draw a diagram

The wall isn't visible as it is kind of within the hedge/jasmine but we've trimmed a hole to try and see what's going on

Good diagram! Hmm. My parents dug trenches with gravel to improve drainage in their loan and create a soak away. However it’s clear that there is some kind of issue from the neighbours I guess. Does the pond have a water feature that may have pipe work leaking?

Thanks I can hear water running into their pond actually but I just thought it was probably an enclosed pump system as she didn't mention it when I said about the boggyness. They would surely have noticed having to top their pond up a lot as well?