In the novel At Bertram's Hotel, The Bishop of Westchester was a guest at Bertram's Hotel at the same time as Miss Marple.
Miss Marple and Selina Hazy met the bishop in the lounge hall of the hotel while having tea. Miss Marple knew the bishop well from his childhood. He was younger than her and had looked after him. She called the bishop dear Robbie like she used to. He responded warmly, calling her "Aunty Janie" and recalled games she used to play with him.
There is a puzzling reference in Chapter 5 where there is a phrase "and the Bishop (dear Robbie!) was dead". Here Miss Marple was reflecting on the thought that many of the people in the hotel did not look real, but then some people she met were real. One was a military man whose name she could not remember. Then Robbie is mentioned after this. One possibility is that this is a misprint and the phrase should read "and the Bishop (dear Robbie!) was real". This better fits the context as she was thinking about some people who are real. The bishop had, after all, recollected accurately a game he played with her and had called her "Aunty Janie". Another possibility is that Robbie is actually dead, and Robbie was not therefore not real, but one of the impostors (she would later discover some examples in the hotel). This is less likely. In the first place, the whole paragraph and the preceding sentence is about some people being real. In the second place, the criminal gang operating the impersonation scheme would not have been so careless as to impersonate a dead person. The whole idea was to throw suspicion on well-known personalities with distinctive appearances.