An editor sent out a paper to three reviewers. One of them, who gave the paper a favourable review, enclosed a research letter on the same topic, with, in his view, a better study design. He told the editor that the author of the paper had encouraged him to submit it during a meeting they both attended. He added that he thought its inclusion would make a good complementary pair of papers. The editor sent the research letter to the two other reviewers who had reviewed the first paper.