Author, political commentator and educator Anthony Seldon is in Washington this week to promote his new book, “The Architecture of Diplomacy: The British Ambassador’s Residence in Washington.”

On Tuesday afternoon, Seldon talked about researching the thinking behind architect Sir Edwin Lutyens’s only building in the Americas. Constructed to look like an English country house with nods to American colonial architecture, the embassy’s design raised intriguing possibilities, Seldon says, including the thought that its portico, with huge Ionic columns opening onto the gardens, was influenced by the White House facade. Research that took Seldon through original documents at the Royal Institute of British Architects, at libraries in Oxford and Cambridge, and to the National Archives never entirely solved that mystery.

Seldon’s greatest surprise? “The way the building still works is extraordinarily clever,” he says, accommodating intimate meetings or gatherings of thousands in the gardens. Lutyens, Seldon points out, was accustomed to designing in vast open spaces, not the oddly shaped plot the British government purchased in 1925 on Massachusetts Avenue and that had to be extended in subsequent years. At the time, “Britain’s power was very much greater, but its relationship with the U.S. was less important.” So the space for diplomatic offices, originally housed in the front wings of the original building facing Massachusetts Avenue, must have seemed generous at the time but was soon “hopelessly inadequate.” Hence the new chancery that opened in 1960 between the residence and the Naval Observatory.

Seldon, who has devoted much of his career to shepherding students through some of Britain’s best-known independent schools, including most recently Wellington College, also talked about American influences on his pedagogy — his admiration for Phillips Academies in Exeter, N.H., and Andover, Mass.; for the “Harkness method” of teaching students in small groups around a table; and the importance of “needs-blind” admissions. He supports the British equivalent of charter schools, has adopted American-style graduation ceremonies at Wellington and encourages students to apply to college in the United States.

The author of biographies of both Labour and Conservative prime ministers, Seldon is completing a book about David Cameron’s Downing Street years. “The Architecture of Diplomacy” follows in the footsteps of two other illustrated histories — of 10 Downing Street and the Foreign Office.