What was the real first name of King George VI?

Our Queen Elizabeth the II introduced mourning attire to be taken on overseas travel because when her father passed she was overseas and arrived back in Great Britain (united kingdom) with no mourning attire and had to wait on the aircraft while mourning attire was sent by royal staff and then disembarked the plane

I know this because the 2 iconic liver birds. are named Bella and Bertie after them. Y.N.W.A.    JFT96

And yet nobody batted an eyelid when Charles married Camilla, or when Harry married Megan, shows how much times have changed.