The late duke, who was fascinated by the topic of alien visitors, was reportedly poised to meet up with one.
Prince Philip's treasure trove of investigative material concerning UFOs has been kept under wraps for decades.
Following the Queen's death, there have been calls for Prince Philip's UFO investigation files to be released to the public.
The late Duke, who died this month aged 99, had long maintained a keen interest in the UFO phenomenon.
Recent reports suggest that the Queen's husband has a keen interest in reading about the UFO phenomenon.