Martin Rees, giving the first of his Reith Lectures (Radio 4), spoke to Sue Lawley about the daily reality of being Astronomer Royal. He must get letters, she suggested, from people who claim to have discovered dark secrets about the universe. "You do best to tell them to write to each other," Rees replied, setting off the first of many chuckles in the audience. It was striking that a Wordle of the lecture, produced as it ended, featured the word "laughter" quite large.

The tone and style were amiable, but the content was serious, tussling with issues about science and public policy, the lack of scientists in government, the relationship between science and the media. Rees argued that we should worry less about low consequence phenomena, and more about "low probability, high consequence" ones, and decried the tendency – say, in the MMR debate – for people to listen "to celebrities, to newspaper people".

This year's presentation urged listeners to debate as the lecture unfolded, and there was lively comment on Twitter. Mostly the response was positive for Rees, and it sparked up when David Nutt asked a question. Lawley referred to him as having resigned. "No, no," he countered, "I was sacked." Rees, going for another gag, declined to comment on what has "come to be called the Nutt Case".