Range Rover SOS System Limited Functionality how to fix. Evoque L538C

I hope this video will help people with the SOS limited functionality message. The principals are the same across the whole range the only difference is the location of the TCU control unit.
TCU means - Telematics Control Unit
Sometimes this can be confused with the TCM which is actually the transmission control module.
Quick tip: if this message appears after the car battery has been flat try running the car for an hour as this can recharge the battery in the TCU.
Fault code U2109-91 will often be stored which relates to the internal battery being flat.