I found this Hurricane picture in a book I'm currently reading and at first glance it looks like an ordinary Mk.IIC, but if you look closely, there's only one cannon coming out of the leading edge of the wing. It looks too small to be a 40mm, so I'm wondering is it a 20mm, and could it be a Hurricane Mk either with just two 20mm's or with a mix of 20mm's and .303cal's?