Immobiliser warning lamp.
This usually flashes when the immobiliser is active.
Obviously the system will prevent the vehicle from starting.
Manufacturer or OEM immobiliser systems are often integrated into the vehicle on board computer system and may prevent starting,ignition or fuelling circuits from operating. Faults can sometimes occur if a receiver does not recognise the signal transmitted by a coded key or remote, or if the remote fails.
This type of system can rarely be bypassed other than by reprogramming.

Aftermarket Alarm and Immobiliser systems are installed as an added security measure by some owners. After market alarm or immobiliser systems can normally be removed by an autoelectrican to enable the vehicle to be started. If you are having an Immobiliser system removed you should check with your insurance company to ensure your vehicle insurance is not affected.