W220 ign lock sticking

Hello gang, I thought it odd last night when the interior light didn't come on after removing the ign key. Now this morning the ign lock won't turn, it seems that the centre ( plunger with red sensor )has not returned out when I removed the key. Any thoughts guys ? Broken spring , clogged up with crud , something busted? I seem to remember that on some cars you have be careful about removing the lock or else the steering lock jams on info in that would be handy. Ta

 

fixed now

simple fix really, 2 small squares of double sided foam tape on the end of the key.
shove the key in the lock. it sticks to the plunger and i free'd it off by pulling gently

happy days,
a new lock £400+...cant do it yourself. plus extra misery getting the car to the garage
a/ it wont start
b/ the ign lock failure locks it into park so you cant push / winch / tow .
it seems there is no steering lock so not an issue

any way .if it happens to you i hope this can save you some grief

thanks to Des at Startech Poole who tolerated 10 minutes of my blithering and made some helpful suggestions