From time to time, in this job, you have the privilege of meeting an individual whose vivid spirit stays with you. For me, one of those individuals was Jeremy Richman, who was among the bereaved parents of the Sandy Hook school massacre in December 2012. I spent a humbling day with Richman seven years ago, when he talked in detail not only about his daughter Avielle – he made of a point of smiling every time he said her name – but also about the work he and his wife, Jennifer Hensel, were doing in her treasured memory.

Both medical research scientists, they had established a campaigning foundation to study the psychosocial factors that created mass killers, “so that other people might not suffer as we were suffering”. In the months afterwards, we corresponded from time to time about the progress of the foundation’s research, in chatty emails.

There was only one subject about which Richman........

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