Rear Fog Lamp for Vintage Cars

According to current legislation in many countries, vintage cars must also be fitted with a fog lamp at the rear.
In modern cars, there is a bit of circuitry associated with the fog lamp switch to prevent the fog lamp from going on when the lights are switched on if the driver forgot to switch it off after the last patch of fog cleared up.
The circuit described here extends that technology back in time. The circuit is built around a dual JK flip-flop (type 4027).