Hymn anachronisms are very common in many British TV historical dramas. In this film, a church congregation sing the hymn 'Holy, Holy, Holy' by Reginald Heber, but use the tune 'Nicaea' by J. B. Dykes, which would not be written until 1861; over 30 years after Cathy's death in 1830 (as listed on her tombstone in episode one).