Hot Potatoe
For the sake of an interview, you certainly don't want to p*** someone off, right at the start! so, as said if it's Lord Jim, then Lord Jim it is unless told otherwise!
Use the title that you are given in the introduction , untill told otherwise.
Personally, I have always struggled with titles and can honestly say that I have never called anyone "sir", just can't do it! It's my red blood
As you can imagine, as a keeper it is often expected. I must admit , that I have never had a problem and if unsure just spoken to the individual directly, without a title. Previous employers with a title have benn called Lord XXXXX or Sir "Christian Name".
I've dealt with royalty to paupers and they are all" Jock Tamsons bairns"
Nowadays, it is unusual of anyone to want a formal title used, beware of those who do.
Incidently, if addressing a Duke, it's "your grace" EDIT, sorry Jimbo, just read your post