Literary efforts whether on page, stage or film involving twins divided by adoption are always popular. Caryl Churchill decided to go one further with A Number, her short piece about the ethics and morality of human cloning.
While it puts the spotlight on to a single "family", the play looks into the wider issue of nature versus nurture in surprising depth, considering its running time is only 45 minutes.
Back in 2006, when he was running Sheffield Theatres, Samuel West had had the novel idea of using a real father and son to play the four characters, named only in the programme to add to the mystery.
West and his redoubtable father Timothy have an unenviable job as they are following in the shoes of two of Britain's most popular actors, Sir Michael Gambon and a pre-Bond Daniel Craig, who created the parts at the Royal Court in 2002.
West père plays Salter, the shifty father who has no qualms about lying to protect his dignity and pride, oblivious of the hurt that he might and does cause.
A Number is a much easier play to watch second time around, as you have more of an idea of who each of the trio of sons is and their relationship, as well as a mental picture of the play's over-arching conceit.
Son #1 has been brought up motherless without being aware that for reasons that are never entirely clear, he has been cloned, perhaps twenty times. Then again, he might as easily be a clone and there lies one of the play's central themes. Who are we and would it matter if we were the real thing or a perfect imitation?
Another is whether cloned products will all be identical. Here, Miss Churchill and Sam W who plays all three come to an unequivocal answer.
That first incarnation, an early but much-loved clone called Bernard is the nervous type, the second who was booted out as a small child to make way for his successor is a bully and another Bernard. Thus, both mirror different aspects of their father.
For variety Michael Black, the third is something of an intellectual with wide-ranging interests and, as such, has nothing in common with the old progenitor that he has never previously met.
With assistance from designer Paul Wills and his lighting and sound colleagues, Oliver Fenwick and Olly Fox, Jonathan Munby sets this sinister production in the round. This is highly effective, as it allows every audience member to observe the actors in close-up, spotting nuances that were less obvious in the original proscenium production, though Sir Michael Gambon in particular ineradicably stamped himself on the memory playing the father.
This may all be a sophisticated intellectual game but in the hands of Caryl Churchill and a pair of good actors, let alone a father and son combo on form and enjoying working together, it will leave audiences pondering the genetic quandary long after they leave the theatre.