The two female Dianas are sisters, born at Newquay Zoo in 1991 & 1992.(or 90 & 91..) I believe they either injured or were responsible for the death of a male introduced to them at Newquay from Port Lympne. They seem to be well settled at Twycross but only one young has been born so far. Its possible they are already both nearing post-reproductivity.
Update- another baby has been born some months ago- I think to the same female as the first one. They are now harder to see after being moved to the old/original Gorilla House where the indoor area is offshow. You have to be lucky to catch them outside.