During his period as a post-doctoral researcher at Oxford University, Roy developed a sensitive method of performing nuclear resonance using a new electron spin-echo sequence which came to be widely used and subsequently known as ‘Davies-ENDOR’. ENDOR is an acronym for Electron and Nuclear Double Resonance, and is a sensitive way of carrying out nuclear resonance for nuclei close to magnetic electrons which are able to undergo electron spin resonance: thus nuclear spin flips are detected indirectly – via their hyperfine interactions with the electrons. In 1970, when Davies-ENDOR was developed, Bill Mims of Bell Labs had already demonstrated an electron spin-echo sequence capable of detecting nuclear resonances and thus performing ENDOR. However, ‘Mims-ENDOR’ turned out to have blind spots, and the Davies-ENDOR approach was developed to counteract this.