The outcome was 2 stripped cogs connecting the fuel pump cog to the crankshaft drive cog. These are sealed by the front cover and fed by an oil spray tube and its suspected were damaged due to oil starvation when the oil pump failed inside the sump which also took out the turbo.

So pump drive was compromised and this explains the DF195 fault code. However still cannot understand how fuel pressure readings were obtained from an empty fuel rail???