Discovered in the collection of Victor Don, a doctor living in Ashford in 1940. He was taking film of his dogs when a dogfight began overhead. Although brief, the film does give a unique record of what is believed to be a fighter engagement during the Battle of Britain.
The shots show the two forces seeking to gain the upper hand as well as an aircraft falling as a casualty, suggesting that this is not a training exercise. At the end of the film is a brief shot of a Spitfire at low level, possibly heading back to base out of ammunition.
The footage begins at 12 minutes 30 seconds. I hope you find it of interest.
https://screenarchive.brighton.ac.uk/detail/5756/