I think I read somewhere that John LeCarre films tend to have "mystery" in their product (the producers)...so that is why not all the actors and/or actresses have their part names included in the IMDb listing..so JN's part will probably not be listed until after the film is in general distribution....or that is my guess.
All you need is love. But a little chocolate now and then doesn't hurt. (Charles M. Schulz)