Most people who research paranormal phenomena choose a side in a war of competing beliefs and disputed evidence. Hilary chose instead the side of scholarship, backed up by the massive home library that he donated to the Archives for UFO Research in Sweden – all 5.5 tonnes of it. His measured approach focused on social and cultural context and human psychology, as he believed that understanding extraordinary phenomena required understanding the person who experienced them. That is not to say he never drew conclusions. He was scathing about alien abductions, for example, a belief he (wrongly) predicted in the late 1980s would never take hold in Britain because people there were too sensible.
The range of his scholarship through time and across phenomena meant he was able to see connections no one else could. In books such as Intrusions: Society and the Paranormal (1982), Visions, Apparitions, Alien Visitors (1984) and Gods, Spirits, Cosmic Guardians (1987), he drew a direct line from, for example, folktales of fairies and leprechauns to modern-day accounts of extraterrestrial visitors. His later books included Outbreak! (2009), which examined cases of mass hysteria, and Sliders (2010), which covered street-light interference, the belief by some people that they turn off street lights as they pass by them. Failing eyesight prevented him from writing down his next book, which he had ready in his head.
The obituary is written by Wendy Grossman, founder of The Skeptic magazine. Note that John Rimmer has a really nice write-up of his memories of Hilary over at the Magonia blog as well.