Some years ago I wrote an article for The Automobile about the earliest Mini based (sports) cars that are known. Both the Butterfield Musketeer, Deep Sanderson 301 as well as the Ogle Mini have all been mentioned as being the first, but you'd be surprised that there have been several earlier attempts, going even back to 1959!
I'd all forgotten about this particular one: the SCG Urbansport, dreamt up by American (!) motoring magazine Sports Car Guide as early as in March 1960. Their contributor Robert Cumberford described it as ‘A dream sportster for the city man’. Cumberford came from the GM design department where he’d been working on the Corvette and would become a highly respected designer and journalist in his later life, designing the beautiful Griffith 600, which would become the Intermeccanica Italia later also. His Urbansport was a Mini based four-seat roadster with a hardtop as an extra. It used pop-up headlights and Italianesque lines. It would have been a great little car, but it never materialized.