This is a Significant Operational milestone.
A significant step in proving the reliability of rotorcraft to the general public. The flight was made by a Cierva C.8L Mk II piloted by Juan de la Cierva. A French journalist, Bouché, was a passenger on the flight.
Source: "Cierva Autogiros | The Development of Rotary-Wing Flight", Peter W.Brooks, Smithsonian Institution Press, 1988, ISBN 0-87474-268-4
For video of the event see the link below,
Source: “The Windmill Plane”, British Pathé website, Issue date: 20 Sep 1928