Imobiliser light when driving

[hipwell]

This has happened twice now on the way home from work.

Driving perfectly fine, then out of nowhere the imobiliser light next to the gearstick will come on solid. If i press the blip on the key while driving it will go out. Doesnt cause the car to cut out or anything..

Also, whats the difference between the imobiliser light on the dash and the one next to the gearstick?

 

[hipwell]

Well I've just realised the light in question is actually the alarm light and not the imobiliser.

What could cause it to arm while driving?