So William Overton approached Herbert Austin about modifying the Heavy Twelve-Four hire car chassis so that it would comply with the London Conditions of Fitness.

In view of the easing of police regulations and the enormous gap in the market left by imported vehicles Austin duly modified their hire-car chassis to suit, and Mann & Overton arranged for their catalogued three standard bodies made in Greater London by: Strachan or Vincent or – for £5 more – Jones.

[3] Because the overall height of the 1930 version[note 1] was much greater than the competition it received the nickname High Lot (HL) or Upright Grand.

Fire extinguisher, horn, number plates, licence holder, taxi sign, Trico visional wiper and speedometer were also included.

Also made by Austin and Carbodies was the hire car FL1 which was almost identical but lacking luggage space by the driver, having instead a bench seat, and there was no roof sign.