“On December 9,  the day before the baby was born, Annabella, with Augusta’s encouragement, consulted with a family friend, Samuel Heywood, sergeant-at-law, on the advisability of leaving the house for the delivery. Either on his advice, or following her own counsel, she decided that the risk of her parents’ discovering that she had left home for the lying-in was too great, and she remained at Piccadilly Terrace. Byron, however, seems to have got wind of this plan and taken it very ill; with labor already beginning, he berated Annabella savagely, and “with the strongest expressions of aversion and disgust” demanded to know “whether she chose to live with him anymore.” Then he left for the theater.
— Byron: Child of Passion, Fool of Fame by Benita Eisler
See also Byron: Life And Legend by Fiona Maccarthy.