The Human Fertilisation and Embryology Act 1990 and the procedures it sought to regulate have been the focus of much comment since it came into force in 1992. While the debates leading to the Act largely focused on the status of the embryo, the Act has, among other things, had a marked impact on how the family is understood. In a recent decision, the House of Lords was called on to determine whether an infertile unmarried man whose ex-partner initially sought and participated in treatment with him, but successfully conceived with an embryo fertilised by donor sperm and implanted after they had separated, was the father of the resulting child. How does the law ascribe paternity to the unmarried infertile man and is the Act and the Human Fertilisation and Embryology Authority sufficiently equipped to regulate this crucial area of health care and family law?