Got in this morning to turn the key and got an air bag light and immobiliser flashing and nothing else… Changed the key - same. Thought it must have dis-charged itself over night (maybe my dodgy hazard light switch) so plugged it in while trying to plan an alternative train journey. Dial read 50% as I had left it last night. Unplugged it and the car/key communicated and I got drive… Note to self - if in doubt, do an earth re-set with the mains to clear a fault!:S
Discharged could be the right conclusion, but not of the traction battery but the 12V. You need power in the 12V to start the car. Although it will take power from the traction battery this only happens when the ignition is on. So trying to charge and turning it on possibly put just enough juice into the battery for you get going.
By the way there is nothing in the key fob so doesn’t matter which key you try.
Glad you got going.