During the Belgian GP, lap 22, just as Button overtakes Schumi (about 105 minutes in if you recorded the whole thing on Sky+), Brundle’s feverish commentary included the words “Stig against Michael Schumacher”, then he immediately reverts back to calling him Button and says something like “Button’s through!”
Was this a Freudian slip by Brundle, who might know who the new Stig is? Check the commentary. He definitely says it.