Woman loses appeal over birth certificate after sperm donor has sex with ex-wife
theguardian.com
theguardian.com
It sounds like all the judges involved are freely admitting that it's a messed-up corner case. And none are claiming that the current laws (for such situations) are optimal, let alone "right".
Not mentioned: All the moral issues around Mr. Informal-Donor showing up again - 7 years later - and wanting parental rights.
Maybe I misread the article or you know details that aren't in it- but it doesn't look like the male "donor" showed up at all, but rather that the mother had a court declare him as the legal parent. I don't think the father has a say in it- so it's not clear that he wants those paternal rights (and duties).
OTOH, phrases such as "F was at that time no more than a means to an end", and "after a separate welfare hearing a judge had given all three adults parental responsibility" would suggest that F has changed his position - actively wishing for a serious parenting role, and also looking (to the judge) like plausibly-good parent material.