The one on the left, naturally... Jenks was a great and knowledgeable commentator, also a man of some courage (anyone who races with his nose a couple of inches off rapidly-moving tarmac is clearly no shrinking violet, which is why Moss chose him to ride in 522 in that epic Mille Miglia). However, this produced a rather blasé view of the dangers of F1, a sort of "if you can't stand the heat, get out of the kitchen" attitude. Wee Jackie was, if I remember the comment in Motor Sport correctly, "a beady-eyed little Scot", when he fought to make the sport safer. I can remember the letters columns of Motor Sport being full of comments on "chicken GP drivers" (probably written by Ford Anglia drivers). Thankfully, times have changed.
If you've never seen it, wee Jackie's fight for safety is well documented in the BBC's Grand Prix: the killer years.