In the novel The Pale Horse, Mark Easterbrook mentions Henry Parkinson as a possible match when Dr Corrigan shows him Father Gorman's list of names. Henry worked in one of the ministries. Mark also knew a Arthur Parkinson.
Later, Mark Easterbrook discovers one "Parkinson" on the guest book of the King's Arms inn at Much Deeping among other names on the original list.
It is never confirmed who "Parkinson" on the original list is. As the names on the list were victims of murder, the name on the guest book is likely that of a relative who wanted him dead.