Daimler Double 6 running problem

Hi everyone my Daimler Double 6 was running great reverse it out of the garage and it started playing up and would start right away but would not rev, tick over was very lumpy, no voltage at the pump with the ignition on, any help, please. Bob

Not very familiar with the 6.0L V12, but try to bypass the fuel pump relay, so the pump runs all the time, and see if the car works.
If it does it’s either the relay, the wiring or the ECU pump circuit.
If the pump is still not getting 12v then the problem is at the power feed of the pump and relay.