The other notable innovation was when the now-legendary steam trail was introduced in 1967. The hot water boiler would be switched on 5 mins prior to the display start time to ensure a full head of steam as the formation started the display.
When Grey 1 called "Steam on, Steam on - GO!", on a moonlit night lucky bystanders could witness the never-to-be-forgotten sight of 24 vapour trails describing a lazy loop as the ghostly Grey Ladies formation soared into the heavens.