I've watched this performance many times already from the BBC series DVD. The song of course suits her vocal perfectly but it is the visuals that make this even more magical. From her little jokey quips at the start as the first strings begin - then you see her facial expression suddenly change as she gets herself set for the song - then somewhat unusually the backing singers and Dusty sing the first few bars together - then a little further on Dusty sings that gorgeous single closed mouth note (hum) (a technique she rarely seemed to use)- And then later in the song the slight fleeting wry smile during those wonderful side on close ups. She never looked better. And of course you could see she was feeling the song and not just singing some words.
....and I forgot to add that at the end the smile as she backed away from the mic that told me that she knew she had just created something very special