As always, Spears is teetering on a tightrope - will she pull it off or collapse like a souffle in a vacuum? - and the tension is delicious.
When she did a backflip during Touch Of My Hand I felt inexplicably proud of her.
Adele premiered her new video, Send My Love (To Your New Lover) at the ceremony. If you've ever wanted to see 10 Adele's super-imposed over each other with the opacity set to 40%, then this is the video for you.
Bieber, DNCE, Demi Lovato, The Go-Go's, Ke$ha and Tove Lo (ft Nick Jonas) also played - the latter being a short, but sexually-charged blast of power pop.
Bbut my favourite performance of the night was the simplest. With no flam or fanfare, Rihanna delivered a vocally-flawless, impassioned rendition of Love On The Brain, bathed solely in a feather boa and a green spotlight.
You can watch the whole thing on 4 Music later tonight.