Steering column lock

[eog]

New to all of this and hope that you may be able to help.
After   resting for some 20 years with 4 owners have now got Fulvia coupe s2 back on the road.
Following an MOT on Tuesday enjoyed some 40 miles of motoring.
Parked up and inadvertently turned the steering wheel without key in lock and locked steering column. No matter how I wriggle wheel and turn key it will not release lock.
Before I revert to drilling out shear bolts on lock any ideas. Have tried small amount of oil, lifted front of car to take load of steering, all to no avail.
I did notice that there appears to be a small hole in the side of the lock that may at one time, have held a small grub screw, now missing. Could this be a retaining screw for the lock barrel.
Any help much appreciated 

[eog]

Rather than leaving this thread inconclusive an update.
Dropped the steering column down and managed to use a centre punch to undo shear bolts.
Lock barrel worn beyond rebuild so ordered replacement from Omicron £65.45 + vat.
Ordered at 3.00pm and delivered by Post person at 11.00am following morning.
Interesting to see on invoice same lock used on Stratos!
I now own a small part of that dream…

[chriswgawne]

Not to mention great service and availability at a reasonable price from our friends in Norfolk.
No connection to the seller.
Chris