I had the same problem on my 560 sel, But I lost the key !!!
The only way I managed to get it off was to hacksaw through the tube section with the steering lock pin inside.
I undid the two 13mm bolts behind the clocks to drop down the steering collom, Then I sawed straight through the tube about 1-2 inches away from where it goes into the steering collom (Its not hardened so does'nt take long)
When u have cut through u will see the steering lock pin inside the outer tube.
Then u wobble the steering wheel left/right and flick out the remaining piece of steering lock pin with a small screwdriver.
A 3-4 inch pin will come out, But u have to wobble the steering wheel to release it to pull it out.
Then u can undo the little hex bolt and push the little locking pin underneath to get the remaining casing out!