House Of Twain - No Button For Cellar?

Hi there!
I've been stuck in "The house of Twain" quest for a while.
I'm at the part where I have to enter the cellar by pressing a button in the dining room. The wiki states : "To enter the cellar, walk into the dining room on the right and then to the servant's area right by the table. There should be a button located on the wall at the end of the room."

I haven't been able to find any button at all throughout the whole room, I've searched every corner possible in the dining room and was wondering if the button might not even be there? Or perhaps I need to do some else first?

 

try looking at this:

 

Yes! Thank you very much for the help :)