Anthony Hopkins is a non-canonical character created for ITV's 2006 adaptation of the novel The Sittaford Mystery. He was an archaeologist working in Egypt some 25 years before the events in the show and whose relevance to the plot would only emerge during the denouement at the end, although his fate can be seen as setting the stage for everything else that happened.
As Miss Marple's investigation and the revelations of Miss Elizabeth Percehouse showed, Hopkins was Elizabeth's husband. Some 25 years before the events at Sittaford, in 1927, he had been an archaeologist attached to the Cairo museum. As a young scientist, he had been determined to prove himself and his research led him to believe that he had found the location of a Zekhen (pre-dynastic) tomb but shortly thereafter he disappeared.
More than 20 years later, 3 years before the main events in the show, a Zekhen tomb was found and excavated and his dead body was found inside. The artefacts inside had also been looted. It transpired that Hopkins had sought the help of Clive Trevelyan, then a soldier stationed in Egypt and an Egyptologist, to verify his research. They broke their way into the tomb (this is seen at the beginning of the show as a flashback). Clive then murdered Hopkins and looted the tomb to fund his political career. Elizabeth knew it was Clive who murdered Hopkins because he had written to his wife and told her he had found a Zekhen tomb and had found someone who could help him verify his discovery. Hopkins had also left his personal effects with the Cairo museum. Elizabeth travelled there and discovered, among other things, a photo of Clive with Hopkins. Between them was a woman, Violet Hopkins, Arthur's sister, would would also play an important part in the subsequent plot.