In the film Patriot Games starring Harrison Ford, the terrorist group uses someone inside the police department to obtain the route & arrangements for Sean Miller's transfer. A few lines and glances by Inspector Robert Highland (played by David Threlfall), riding in the van, seem to indicate that he is on Sean's side, or at least understands the IRA cause with the following lines:
Although I disapprove of the things ye've done, Sean, I can't quite bring meself to condemn ya. I can't... because I understand where the hatred comes from. I more than understand it.
When the van comes under siege, the officers don't seem to know what's going on, while Highland just keeps looking at Sean as if they both know exactly what's happening. The two officers then wish to hold out for backup, yet Highland orders them to open the doors. During the discussion afterwards, group leader Kevin O'Donnell seems to believe that Highland is an honest cop, asking him how much the English pay him to turn on his own people (Highland is Irish). O'Donnell then hands a gun to Sean Miller and
Miller promptly executes both Highland and the two officers that were in the van.
I haven't read the book, so I'm not sure about the nuanced context here. The lines may simply be Highland attempting to turn Miller so that he'll testify against the rest of his group, but the glances between them - and the actions of Highland himself - don't really make as much sense in that context. Surely the book would explain such details better than the film.
Was Inspector Highland their man inside (and his fate was only to show how insane Miller is) or was he an honest cop?
And, yes, I realize that a different inside man was revealed at the end of the movie. That doesn't preclude the Inspector being one also, though, or at least an IRA sympathizer/mole. Highland's fate also foreshadows that of
terrorist ally Dennis Cooley, who is also executed by Miller.