That is wonderful. Brought back lovely memories of when my mother's cousin used to visit us - in winter it was always a Jaguar (initially a Mk2 and later an S type) and in summer a Vincent HRD.
The film was made by the Production Engineering Research Association (now known as Pera) - based only 12 miles from here in Melton Mowbray.
Just compare the 1960's assembly process with the 21st century version in the Tesla film recently shared on TM!