I've never bumped the gear selector while rotating the steering wheel on my Silver Shadow 11 but a friend of mine once accidentally bumped it when getting out of the driving seat. Could you post a photo of your steering wheel/gear selector so we can determine if something is out of line?
I've brightened your photo a bit so I can see the gap more clearly. It does look very close. The distance between the gear selector and the steering wheel in my car, taken at it's closest (P) is 2 1/4 inches, however my car is a 74 "series 1". I cannot imagine the engineers would reduce that gap for the series 2. (or maybe they did).
The two pics below are of your car and mine. (Yours looks in great condition)
On both of my Shadow 11s the closest the gear selector lever gets to the steering wheel is 2" and the furthest away 2 3/4" .
If the selector lever mountings are where they should be and tight, then I would suspect the selector lever has been bent if your measurements are less than this.