What's causing the damp patch under window sill?

[KatieM_13]

Hello! I recently moved into a flat and a damp patch has started coming through under the window sill. Looking out the window, it looks like a drip is coming down from the gutter and landing on the window sill, and then dripping down from the window sill. I initially thought the gutters might be blocked but I just had someone round to check and they're fine. He thought it might be the roof felt overlapping the guttering that could be the issue (see image)

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I'm really not sure anymore what the cause of the issue would be. I've attached some photos and was hoping someone might be able to advise!

 

[23vc]

Is that a valley discharging into the gutter? It’s probably overshooting/overloading it.

 

[23vc]

And even if not blocked, could be the seals on the gutter outlet causing it to drip, does look a bit old

 

[KatieM_13]

Thanks for your reply! Yes, that's a valley going into the guttering then. That does sound like the most logical explanation. I'll get someone round to look at it