There's a strange object in my render and I just can't find it in my scene!

This is driving me mad. I’ve double checked everything and can’t find the large grey object that appears in my render.
Just wondering if anybody had any ideas.

I’m trying to tinker with lighting at the moment and I had one success (pictured below).

Then I increased the size of the glossy walls and this appeared…

Here’s the .blend file if anybody fancies a look.

You are seeing the camera clipping the view
Extend the camera clipping end distance so it falls outside your scene

That worked perfectly. Thankyou Richard!