Zona-rapida blogspot nailed it! They posted a terrific gallery of Bernard Cahier (the photobombing photographer)

With Kirk Douglas at Monaco, 1970

the move that really made him famous, passing cold drinks to drivers

http://zona-rapida.blogspot.com/2016/04/fotografia-bernard-cahier.html
http://www.f1-photo.com/

I posted about him 2 years ago, when learning about his silly antics from Denise McCluggage  http://justacarguy.blogspot.com/2014/08/the-grand-prix-photobomber.html