Cleaning 5D3 mirror

[digital]

It looks like I've got a speck of something or other on the mirror of my 5D3. I can see it at about 10 o'clock in the viewfinder but there's no sign of it in any images.

So, two questions...
- what's the best/easiest way to remove it?
- if it's at 10 o'clock in the viewfinder, where should I look first on the mirror?

 

[woof woof]

If it's on the mirror wont it be reasonably easy to see? If it isn't easy to see it's possibly more likely to be on the focus screen or in the VF.