This is actually a Brown Wood Owl (Strix leptogrammica). If I recall the Ninox are in the aviary to the right of this - the labelling in this area is not always very clear/accurate.
I don't know if Twycross' Ninox are boobook or novaeseelandiae, and I strongly suspect the European zoo population is a mix anyway - the names seem fairly interchangeable.
The only place I've ever really trusted on this front was Niendorf (Timmendorfer Strand), where they had both forms amongst their ridiculously huge owl collection.
Thanks Maguari......I knew I was adrift somewhere!
This photo was taken 10 years ago and the labelling has probably improved since. The aviaries in my pictures looked very similar but I obviously didn't take a picture of the Brown Wood Owl sign (and they are not mentioned under current species on Twycross website).
