Björn and his wife Christina attended this Elton John and Brandi Carlile concert at the London Palladium in London. 

Dan Levy was the host.

It looks like they might be in the second row from the front of the stage with Björn on the right looking out from the stage.  It would seem there were no close-ups of him/them.
Hence, I'm only adding two clips here (I'm Still Standing and Swing For The Fences) as you can barely see Björn.

View the whole concert here (might be UK only).
An Evening with Elton John & Brandi Carlile - ITVX

YouTube link c/o Elton John HD Collection