Of course that's 10 inches, dear!
The first, and largest, floppies were 8 inches, first marketed circa 1971 when Jon Pertwee was Doctor Who. There were a lot of variants, with soft versus hard sectoring, double sided versus single sided and several recording densities being differentiation points.
Circa 1976, during the Tom Baker years, Wang requested a smaller, cheaper floppy which drove the development of the 5.25 inch format offering similar variations to its bigger cousin. You could also physically hack a single sided 5.25 inch to become a flippy.
In early 1980s, many smaller variants were developed until everyone settled on the 3.5 inch format and Peter Davison.
The point of all this being that there never was a 10 inch floppy. There were some specialist 10, 12 and 14 inch optical media dating back to the 80s. Perhaps Officer Plod saw a 3.5 inch drive and made an understandable mistake? I blame the metric system.