I use a Sten - it has a broad, bright light which is evenly spread.
Don't use a Raptor or anything that confines the beam.
Also don't bother with a Petzl duo or anything similar as you won't get anything decent from it.
It also matters where you are filming - if you are in a slate mine alone - forget about video. You need a LOT of light to get anything half decent in the chambers (A party of 4 or more isn't bad). If you are in, say, a lead mine, you will be fine as long as you don't have a confined beam.
I was considering a GoPro camera and would be very interesting in seeing your results if you wouldn't mind popping something on youtube 😉
Ian
A door, once opened, may be stepped through in either direction.