Jen that was wonderful.
I went to the Coupes Moto Legend several years ago when it was held at Monthlery (sp?) near Paris, a French Brooklands.
The featured marque was Benelli and they started one of the GP racers up with a large crowd around it. I was in about the same position as that video was taken from.
When it fired up on the rollers, the entire crowd jumped backwards together. It had no tickover and was revved between about 3000 - 9000 rpm for a couple of minutes by an old guy in mechanics overalls who was obvioulsy stone deaf. Every single person in the crowd had both ears covered.
God knows what they must have been like to race against, you do not want to be behind one for very long.
