[mylesdw]

I think the pedal needs to be UP if you want to bleed by gravity; it is the only time the reservoir is directly connected to the wheel cylinders.

What sort of braking system is it? Is it air/hydraulic (see picture) or vacuum/hydraulic? I'm guessing the former for a diesel-engined vehicle in which case pumping the pedal up and down will have no effect without air pressure in the tanks.

Bleeding by gravity alone is probably not practical due to the twists and turns in the pipework (especially front nearside).

There are various tools you can get that (slightly) pressurise the reservoir and these work well.