Walter, as any Trumpologist knows, was the self-appointed family historian and enjoyed sharing family lore and memorabilia with journalists. He had assumed this role by virtue of his close relationship to the family: He was the son of Fred Trump’s older sister, Elizabeth, who had herself served as Fred Trump’s bookkeeper early in his career as a builder and developer. When I was working on my Trump family biography in the 1990s, I met with Walter in a modest office that was down the hall from Fred’s own longtime quarters at Beach Haven, a government-subsidized apartment complex near Coney Island that Fred had built nearly half a century earlier. Walter, it seemed to me, doled out bits of info in a somewhat gloating way.

For many years, during the long stretch of time when his younger first cousin Donald was a regular on the gossip pages of the New York tabloids and then the star of “The Apprentice” TV show, there wasn’t much demand for Walter’s archival services. Donald Trump was master of his own narrative. That changed when Trump ran for president and soon Walter was the increasingly beleaguered target of an almost unending stream of media requests. By the time his cousin had become the surprise 45th president, Walter had all but resigned his unofficial job. As he said to Michael Kruse in the summer of 2017, “I’m not doing anything. I’m letting Donald do his thing. I just can’t get involved and give information that always comes out wrong … I promised everyone I’m not going to do that.”

Now, Walter’s assiduous work as an amateur historian appears to have become a major source for the Times’ blockbuster piece.