well, on most cars I have worked on there is a small hole some were on the case of the barrel that you can insert a 3-4mm drill bit then turn the key to ignition and the "key part" then withdraws, I have not found any hole on the casting to insert a drill bit,and the actual casing is secured to the column with sheer bolts that are designed (and have) broken of when they were fittied. I could chisel the sheer bolts loose have done that in the past, but its a real pain !
I think myself competant with the spaners, swapped engine on sunday and axles this week, its just when i find something hard its normaly cos there is a knack that some one else knows and can save me ages....