"German hating" might be a bit too harsh for what I've read about him and his dislike of Germany. But it is easy to see why a British born in 1911 may not have had too many fond memories of Germany and Germans and why these memories in 1963 were still quite vivid.Rumours are, by the way, that the sketch was written with Admiral von (van) Schneider (one of the 'guests' Frinton impersonates as Butler James) saying 'Prost' to Miss Sophie and that Frinton remade that to 'Skoll' (skål) in order to avoid that German (Latin) word.
Wolfgang