Brian Bedford is marvelous as the man who shows up at the Everett's living room window and announces cheerfully that he has come to marry Nanny. Alone at home with "Chumley Fenshaw," the Professor is consistently frustrated when Chumley finishes his sentences, when Nanny announces she is engaged to him but wasn't expecting him to turn up "this year," and when Chumley gifts each of the children with even more pets for the household. Chumley's happy and confident ways leave the Professor unsure of how he feels about the whole thing, especially when Chumley asks him to give the bride away and the family is forced to deal with the prospect of Nanny leaving them. A lot of fun in Bedford's depiction of Chumley, in Richard Long's string of facial reactions to his frustrations and facing his feelings, and in Juliet Mills's managing to deal with both of them happily in the end.
An aside - Richard Long died less than three years after Nanny ended. I've often thought that if this show had still be in production when he passed, having Nanny go ahead and marry Chumley, with the professor leaving them as his children's guardians, it would have made a pretty good show of its own - two magical people raising children that included an oldest son who was scientific and fact-based. Not that Richard Long could have been easily replaced, but a new twist to the show would have been interesting in itself.