TD5 Defender Won’t Start, ECU?

Hi,
Today was the day my Defender decided to die on me... my mechanical knowledge is but and bolt based and sadly this isn’t a nut and bolt fix.
Car - Defender 110 TD5 2004
No prior issues but car won’t start. Drove to my destination fine, when I went to fire her up to get home it just turns over and doesn’t fire. On the way I did hear what sounded like something fall off and hit the footwell, couldn’t see anything obvious on the road and was driving under trees so assumed it was a branch - car continued to run fine.
Fuel pump does not run - I have tried wiring the fuel pump relay so that it would run which it did but the truck still won’t start. There is, as with all TD5’s, oil residue at the ECU so will clean that out tomorrow. Have also read that a flywheel sensor Issue will stop it from
Starting - perhaps what I heard fall off? Although I assume it would have cut out straight away.

Any suggestions or advice? Not looking forward to a new ecu and programming bill...

Cheers.

Try posting in the defender section more gurus will read it there...

You really need to plug it in to a Nano or Hawkeye. What condition is your battery in? My Td5 did this when the battery was knackered. It didn’t outwardly seem knackered, but caused the immobiliser to kick in due to voltage drop when the starter kicked over ( well thats my theory).
Get the battery tested and if its bad or tired, fit a new one that will suit a Td5. 900cca i think.
But i dont even know if defenders have immobilisers! Check your ECU loom for damage also