Good little video Ed,
This is where Constant motion casting started, kinda like a Spey/Belgian cast, if anybody doesn't know about the Belgian cast, its worth a google.
Grant in a letter to Jock Scott using his Highland Switch cast c1896.
Now some observations regarding what I call and mean by practical
fly casting. When casting on the Thames I called my cast a modification of the 'Spey' cast. Critical observers there called it the 'Planet' cast. Arthur D.Craeshay (Silver Grey) called it 'perpetual motion, for the simple reason that it was done with a tight line from end to end and not an atom of time lost in its delivery'. I was unconcerned what they called it and allowed them to call it what they chose. In any case it is the natural and practical cast, adaptable under whatever conditions a fisher may happen to find himself at the waterside, with trees or rocks in close proximity at his side or behind him and getting out a correct line, longer or shorter according to the position, and, if the obstructions are four or five yards away, he has full freedom, as though on the top of a mountain.