During 1949, Joe Trenaman in the BBC’s Further Education Department conducted an experiment into listeners’ comprehension of science broadcasts (and some non-science broadcasts). Subjects listened to a recorded broadcast and then wrote everything they recollected. Their recollections were marked and correlated with their educational qualifications and level of interest. The major findings were that subjects who understood the talk best were not the ones who found it most interesting. Rather, the subjects for whom the talk was only just comprehensible found it most interesting. This ‘scientific’ test of comprehension had a number of outcomes for the various interested parties. Trenaman conducted further experiments and eventually become an academic educationalist. For the BBC, the findings supported existing institutional practices, in particular the three-service network that had been developed just after the Second World War. For scientific advisors to the BBC, however, the findings played into a current debate with the BBC over the form science broadcasts should take. Trenaman’s results were announced just as scientist-advisors were on the defensive, having had their claim that science broadcasts concentrated unduly on ‘social issues’ disproved by evidence from BBC managers. Trenaman’s findings were used by scientists to support their argument that science broadcasts should be managed by an outside scientist, who would ensure that they adhered to requisites of comprehensibility and scientific coherence. The outcome was the experimental appointment of a coordinator for scientific broadcasts. The episode can be seen in the context of long-running contention by scientists that the BBC had a duty to privilege science in BBC output ‘in the national interest’, and the BBC’s equally long running resistance to such external scientific pressure.