What holds up this part of the landing?

[VioletG]

We are taking down stud walls in our victorian property. They were added in the 80's, but we are confused by the stairs.

In this pic you can see the frame of the stud wall we removed, part of the frame is sitting under a 'penisular' part of the landing. Next we want to remove the frame. Obviously the frame wasn;t there originally, and you would see the upper spindles from downstairs. So what supports that part of the landing?I don't want to remove the frame and discover it supports the upper landing.

So basically, in the pic, there should not be a wall on the left of the rail on the turn set of stairs.

 

[blup]

The original staircase will be supported by stub joists at the mid landing which form part of the staircase structure itself. If these weren't removed the stud wall itself wont be structural.