The Austin 12/4 was introduced by the Austin Motor Company in 1921. It was the second of Herbert Austin's post WW1 models and was in many ways a scaled down version of the 20/4, introduced in 1919. Initially available as a Tourer, by 1922 three body styles were offered, these being the four seat Tourer, the two/four seater (both at 550 GBP) and the coupe at 675 GBP. The car enjoyed success throughout the vintage era with sales peaking at 14,000 in 1927. While the mechanical specification changed little (engine increased from 1661cc to 1861cc in 1926), many body styles were offered with saloons becoming more popular as the twenties drew to a close. The car continued in the Austin catalogue until 1935 and as a Taxi option until 1939. The last cars were produced for the War Department in 1940.

During the thirties, the car began to become known as the "Heavy 12", to distinguish it from the other 12HP cars in the Austin catalogue ("Light 12/4", 12/6 etc). Today, the Austin 12/4 is remembered as being virtually unburstable and is well catered for by the Vintage Austin Register in the UK and various other clubs in other parts of the world.

The 12/4 is also reasonably well known to children in the form of 'Gumdrop', the title character of a set of book authored by Val Biro, who owns an example. Gumdrop is at one with other magical British cars such as 'Chitty Chitty Bang Bang' and James Bond's Aston Martins with his magical buttons, and personality.