Thanks 55rsturbo.
Here’s some more information I discovered today.
The independent garage I took the car to took it to Ford for testing. This revealed a fault code that indicated the injectors were faulty. I asked what the code was and was told that they would need to check with Ford because the information wasn’t retained by my garage.
Now that the injectors work a new fault has been revealed, a mechanical one. Electronic faults have now been eliminated.
The guy I spoke to at the garage dealing with my car said he trusted the diesel engineers that processed the injectors, that they have a good reputation.
I asked for more information about the diagnostic process that was followed. A compression test was done and one cylinder was found to be low, but not enough to be causing the problem. The fuel pressure was fine. A leak off test was inconclusive because the engine wasn’t running well enough for it to be reliable.
It was suggested on this or other forums that the problem might have been a bent con rod or jumped timing chain. I was told by guy at the garage that if either of these was the case then the engine wouldn’t run at all.
To determine the nature of the mechanical fault would entail taking the head off. Is this a big job? Of course, there’s no guarantee that what is found would be economical to repair.