Ignition barrel or auto gearbox fault?

[aston]

Hi all, I have a W124 Classic Mercedes ce220(1993) which is my every day car I parked the car Friday after work, Went to start it today and noticed that the key would not go into the barrel. Something was stopping it, (I did notice recently that it would go in one way but not the other) Anyway i forced it into the barrel but it will not turn at all. So i have now filled the barrel with WD40, put the battery on smart charge and sworn a lot. Now I do remember on an Audi i used to own you couldn't turn the key unless the shifter was in P l position? So maybe the car believes that the shift is elsewhere?
Does anyone have any ideas what the problem could be as something niggles me that it is not the barrel at fault.....
Thank you