Wood burning stove leak

[Gac2112]

Hi, I’m not sure if I’m posting this in the right place but hoping someone might be able to help.

We moved into our house a couple of years ago and there was already a wood burning stove in the living room. We recently had some brick slips installed on the wall behind the stove. Since then, we have had water leaking in at the point where the flue/chimney pipe goes into the wall to vent outside. The water is a brown colour so I’m assuming that means it must be coming down the flue?? There was never a leak before the brick slips were installed. The people who installed the brick slips were from a heating centre and HETAS registered. They’ve been out twice since the leak started to try and fix the problem but nothing they have done has worked. I think they’re at the stage now where they’re not really sure what the problem is so I’m trying to figure it out to see if we can fix it instead. I’ve attached some photos to try and show more clearly where the water is getting in...does anyone have any advice on how/where this water is coming in?? Any help massively appreciated. I’m hoping to avoid having to take all the brick slips back off again but it’s looking more and more likely that we’re going to have to in order to sort the leak

Thanks to anyone who replies.

 

[SpecialK]

What is on the top of the flue? Is there a cap? Can you post more pictures from outside and further back from the flue inside? Is the pipe coming through the wall angled?
The flue should interlock sending any water down to the woodburner. Its possible this is tar from wood running down but it should end up in the woodburner...?