Wow! The Vortex cutting disc was already designed by 1977!
That was a very revolutionary year in many ways. Saturday Night Fever and Star Wars were released.
Seems appropriate to have this futuristic but ultimately short lived design come out then. To think they were still making the Mayfair chassis at the time.
Work was to start on the drawing board two years later, for the powertorque that was to power it.
There was already an artist's impression of what the Vortex mower would look like by 1979.

Ahh, if only victa had kept producing the thumblatch catcher series, they would be in better shape today!