Aubrey Prior was a geneticist, and the "father" of Vanessa Prior.
In 1973, he led an expedition to Egypt where he found Nephthys tomb, and uncovered the second mummy which the Fifth Doctor had hidden. He brought it and much of the tomb itself back to England. After performing a CAT scan on the mummy, some of Nephthys' psychic power was released. This enabled Sadan Rassul to gain influence over Prior. He made Prior take cells from the mummy, which was that of his daughter with Nephthys instinctive half imprisoned within it. Prior created a clone from the cells, and raised her as his daughter, called Vanessa. When she turned 21, Nephthys consumed Vanessa's mind. No longer of any use to her, she killed Prior. (PROSE: The Sands of Time)