Composers are much more relaxed about self-plagiarism than scientists. It was practised by the best: take Bach's Christmas Oratorio, which recycles several of his secular cantatas, and Mozart's Mass in C Minor, which was transformed into his Davidde Penitente.

As for Handel, he was prone to reproducing his own and his colleagues' music with equal nonchalance. His love duet 'No [pause] di voi non vo' fidarmi' becomes 'For [pause] unto us a child is born' in Messiah. Same music, different atmosphere.

Some scientists might also defend self-plagiarism on the grounds that the data are the same but the conclusions are not. Even my venerable professor of biochemistry, when I chided him for setting his students the same exam questions he had asked us 20 years before, replied tersely, “The questions are the same, the answers are different.”