Sir Adrian Boult explains his conducting technique (video)

From a BBC documentary on Sir Adrian Boult (1889-1983).
I am an ardent admirer of Boult's interpretations.
Peter Heyworth wrote in The Observer: "From Arthur Nikisch he had early acquired an immaculate stick technique and was quietly scathing about conductors who used their anatomy to indicate their artistic requirements. [...] In an occupation ridden with inflated egos and circus tricksters Boult brought a rare probity to everything he undertook."
It is interesting that when one observes his conducting style, from the outside there is always calmness, elegance, self-control and economy of movement and gesture, but with this style he often achieved great results with the orchestra characterized by a warm, refined, living sound, full of expression and fire. Behind every work he conducted there was immense knowledge and thoroughness.
I think these principles also hold true for many of the truly great pianists of the past.