(12 May 2005; Lord Nicholls of Birkenhead, Lord Steyn, Lord Hoffmann, Lord Hope of Craighead and Lord Walker of Gestingthorpe; House of Lords)  2 FLR 843,  The Times May 12
The mother and her unmarried male partner sought fertility treatment involving donor sperm and the man signed a 'male partner's acknowledgement', acknowledging that he intended to become the legal father of any resulting child. By the time the treatment had resulted in a pregnancy, the couple had separated, although the mother had concealed this from the fertility centre in order to continue with the treatment. When the child was born, the man obtained a declaration of paternity, but the Court of Appeal allowed the mother's appeal. Adopting the reasoning and conclusions of the Court of Appeal, the House of Lords held that in conferring the relationship of parent and child on people who were related neither by blood nor marriage the rules must be applied very strictly. If, as in this case, the 'joint enterprise' of fertility treatment had ended by the time the successful treatment had begun, because by that stage the consenting couple had separated, the man was not the legal father of the resulting child.