In October 2006, May re-registered for his PhD at Imperial College and submitted his thesis in August 2007 (one year earlier than he estimated it would take to complete). As well as writing up the previous work he had done, May had to review the work on zodiacal dust undertaken during the intervening 33 years, which included the discovery of the zodiacal dust bands by NASA’s IRAS satellite. After a viva voce, the revised thesis (entitled A Survey of Radial Velocities in the Zodiacal Dust Cloud) was approved in September 2007, some 37 years after it had been commenced. He was able to submit his thesis only because of the minimal amount of research on the topic during the intervening years and has described the subject as one that became „trendy” again in the 2000s. He graduated at the awards ceremony of Imperial College held in the Royal Albert Hall on 14 May 2008.