Engine goes to limp and then stops after few miles
 

My LR4 2013 diesel drives wonderfully until the other day I was overtaking. Then it went to limp mode. In a few days, it was good except I could not do a full throttle. Now it drives maybe 20 miles and dies out. I wait a few moments and can drive it again carefully. I know this as my garage is 250 miles away and it took me 8 hours.
The computer says fuel pressure and I've changed the diesel filter 10 days ago.
what can be wrong?

Update - Had another read on the computer - P0087-21 Fuel rail/system pressure - too low.
When the engine is checked it has NO PRESSURE, but it starts and runs for a while.....
Is it the Pump or a faulty sensor ??