What could have caused this damp patch?

Sapindus

Surveyor found damp readings in the lounge and noted this damp patch (2nd picture, on the right just above the skirting).  The other side of the wall is a blank wall next to kitchen cabinets.  The end cabinet the other side of where the patch is, is different to the other ones but not in a way that looks like it has been bodged in to hide something, because the worktop all matches up.  I pulled the plinth off and could see clean skirting board at the back.Just in front of the cabinet corner is a metal tube protruding slightly from the floor.  I thought maybe it was a pipe that had been cut off but it looks too chrome-y and the estate agent suggested it could have been a pole supporting a worktop etc.  It doesn't make sense to have been a washing machine or dishwasher.  
The surveyor of course has recommended calling in a damp specialist.

What do people here think?

Mark_d

Maybe someone cleaned the all with a wet sponge!
If there was a damp problem there I'd expect it to be reflected in the skirting board.

Sapindus

The surveyor does say "damp affected skirting boards".  But I put my hand on the damp patch and don't remember seeing anything particularly noticeable about the skirting.

The surveyor when I spoke to him did not seem terribly gloom and doom about it.  The house has been empty since last summer. 

FreeBear

Left hand side of that patch has an uncharacteristic straight vertical edge - In line with the edge of a sheet of lining paper perhaps. Possibly staining that has given false readings on the damp meter ?

Yes, it requires closer inspection, but with an open mind. So don't go for one of these "free" damp surveys or you'll risk finding them diagnosing rising damp along the whole length of the wall to a height of 1m.

Grumpy_chap

Something that localised is likely to be a leak from a pipe buried in the wall.
Do you have a pipe detector that you can rub over the wall to see where pipe are routed and then use that to try to work out what could be there?  Possibly a redundant radiator pipe.  Possibly a water pipe.  If you can trace the pipe, you may be able to find a point to access the pipe and isolate (if not required live) without needing to gain access directly in the wall.

Stud / pipe / cable detectors can be quite low cost:
https://www.amazon.co.uk/Draper-13818-Metal-Vage-Detector/dp/B003D07CQ4?
I cannot recommend any specific product.

LHW99

Definately damp, and not oil? or some other spill (tea, coffee)?

Lorian

That straight vertical edge of the patch lines up with the left hand vertical side of the right unit of the 4 sets of bookshelves* that used to be in front of that wall. I suspect something was split on the shelf unforseen.

 It's a little brown maybe for water too.

Personally I'd smell the wall there for a clue.

*Check the indents on the carpet.

Sapindus

Obviously I am looking for the answer that enables me to feel justified to buy the house and sort this out later, not the answer that says "all the floors are rotten and it's going to cost you thousands run away now".  But these answers have made sense, thanks! (The floors are concrete.)