Electrically dead

[Lanark]

Hi all
The other day I drove 350 miles. The first 100 with headlights and heated seats on. The car started no problem.

Another 150 miles, again started no problem.

After the last 100 miles I stopped and tried to re start and the battery was completely dead. I jumped the car from another battery and it started ok.

The battery is a month old, and has since been recharged to 13.5V.

When I try and start the car, the dash lights come on and after a few seconds a message about an airbag fault.

When I turn the ignition, the Rev counter and speedo rise a little to just above nought.

There is no clicking of the solenoid. The starter does not engage. Nothing happens to attempt to start the car.

When I try and start from another car, I get the same Result, so it's not the battery.

It's as if it's immobilised, or a solenoid is stuck.

It locks and unlocks of the key fob, remote function.

Any ideas?