What Americans Call a "Rumble Seat"
This odd period-style accessory is a "four-seater" conversion introduced in 1957 by Scottish MG Distributors John Gibson & Sons Ltd. from Edinburgh. They did it for a local farmer, and the car’s registration number was RSF 456. The spare tire goes on the trunk lid. Passenger feet go through an enlarged hole in the rear bulkhead panel. If you're going to put two people in the MGA's boot, they would surely be very friendly (or very small). Could be a mad rush though.