In the 1970s, IVF babies were - as Neville on Auf Wiedersehen, Pet said of sex in Gateshead - in their infancy. Fertility treatment was becoming more common, however, and one of the results was a rash of headlines about miracle sextuplets. I have an irritatingly untraceable memory of an exploitative one-off ITV sitcom of the time, in which a cynical father came to terms with the news of his wife's multiple pregnancy by doing a deal with a baby-food company to use the resulting children in commercials. The punchline was that when the babies emerged they were black, making a cuckold of the white husband and, by implication (for this was many years ago), thwarting his fantasies of wealth: who would want to see six black babies tucking into jars of Cow & Gate?
This was what passed for comedy in the 1970s, but there is no escaping the comic dimension to the idea of a white couple unexpectedly giving birth to a black baby. At least, I thought there would be no escaping it, until I watched Born With Two Mothers (21 April, 9pm) and had to hold myself back from adding my tears to those that drenched much of the cast much of the time.
The story began with a mix-up at the fertility clinic, a mistake that resulted in a woman who was desperate for a baby being implanted with the embryo from another, equally desperate couple. The dilemma was who should keep little Joe: the birth mother or his genetic mother?
When Louise Brown, the first "test tube baby", was born in July 1978, we could hardly have thought that, within a generation, the procedure would become so common that such mistakes could be made in haste. But, the programme assured us, there have already been several such cases. Because the frightening secrecy surrounding family court proceedings makes it impossible to follow a real case, the producer Oliver Morse had the idea to explore the issue in a drama-documentary. So, this story was fictional and the two couples were played by actors. Yet the responses to it came unscripted from real lawyers, doctors, social workers and the judge who would decide on custody. No one, not even the writer, Zinnie Harris, knew what the judge would decide.
The dilemma of custody, although appalling for all sides, is not, in fact, so hard to resolve rationally. What should surely happen is that the baby should be passed as quickly as possible to its genetic parents, the birth mother who has carried the child should be compensated financially (a million might come somewhere near to a recognition of her time, suffering and loss), and the clinic should be fined.
The law, however, lags behind genetic science and favours birth mothers unless challenged in court. This is the worst of all possible worlds, because the legal process takes so long that by the time a judgement is made, the birth mother and her partner will have bonded irreversibly with the child. The case becomes not a question of legal ownership, but a beauty contest to decide who would be the best carers. Bruno Bettelheim's modest concept of the "good enough parent" - which is probably the most that society is competent to judge - is thrown out in favour of a judgement that would have taxed Paris.
As you can tell, Born With Two Mothers made me think. It also moved me, but I wonder if this was despite rather than be-cause of the programme's hybrid format of part scripted play, part improvised drama, part documentary and part reality TV game show. What made it work was that, beneath all the other elements, there lay the foundations of a sturdy and tightly plotted drama no less manipulative for being understated. For example, although the story needed to have a white and black couple in contention with each other - after all, who'd believe that an IVF clinic would come clean if its mistake involved an embryo of the same race as its host parents? - it cleverly made the couples very similar socially, economically and emotionally (both women's need to become a mother was expressly pathological). They even lived, for goodness sake, in virtually identical houses.
Within such a tightly controlled dramatic context, I felt sorry for the real-life professionals, impaled upon the horns of a dilemma finely sharpened by the scenario-makers and the heart-rendingly honest performances of a dream cast that inevitably made them look wooden. Lennie James, an actor I admire more every time I see him, played Errol Bridges as a man filled with the righteousness of his son's black destiny. His speech to the judge at the end truly did not seem a performance, more an act of self-expression. As his wife, Sophie Okonedo (Oscar-nominated for her performance in Hotel Rwanda) used her beautiful, heavy-lipped face as a canvas on which to relay every tremor of emotion.
Okonedo was matched, on the other side, by the always wonderful Lesley Sharp, who proved the maxim that love, even maternal love, is a form of madness. My favourite moment was when her consultant told her of the "very slight chance" that the baby she was carrying might not be hers. Sharp chose to break not into tears, but into a grin of disbelief. By acknowledging the situation's potential for black comedy, she precluded it. That's acting above and beyond the call.
Andrew Billen is a staff writer on the Times