Graham, First check injectors for leakage back into the spill pipe, easy test and could save you a little time. I suspect this vehicle was driven and then wouldn't start. To test injectors, remove spill pipe and clamp off the spill near the return line. Have someone turn on the ignition and watch the top of each injector, if any fuel comes out regardless of how small an amount, that injector is duff. I have posted this before and as I said, the high pressure pump is just that but not a high flow rate, so pressure drops in the common rail and the pump cannot catch up whilst cranking because of the injectors being pulsed. May save you some time, worth a go, I have had a few of these lately and on Merc systems too.