What *Was* The Green Cross Code?

Green Cross Code

Yesterday, I saw a tweet from 80s Nostalgia which asked what the exact Green Cross Code was (apparently to solve an argument)

Now, as a fully-fledged member of the Tufty Club and proud to be born in the 1970's, I jumped straight in with
"Look right, look left, look right again..."
because we all know that you have to check the oncoming traffic first and the UK is a driving-on-the-left-hand-side minority country, isn't it? And then, just for shits and giggles, I thought I'd check out the retro adverts on good old YouTube.

Well, my ghast is still flabbered!!

tufty badge,
Not anywhere in those three videos does Darth Vader The Green Cross Code Man say those actual words.  Neither does Tufty, although members were obliged to wear their badge on the right hand side to remind them to look that way first, and it's not even mentioned in SPLINK (what do you MEAN you don't know what SPLINK is? Find out here)!

So help me solve the mystery... where did the words, "look right, look left, look right again" come from? It can't be a 1970's urban myth, can it?