The princess should have been the top selling car, but the stupid decisions made by BL messed things up. First they decided not to have a hatchback so as not to take sales away from the maxi. Also they didn't use the 4cyl E series which would have fitted an gave the car a 5 speed gearbox.
What they should have done was deleted the maxi at this time,which with hindsight probably shouldn't have been built in the first place, as it was basically taking sales from the 1800, and as for the three litre... Well a car that was smaller inside than the 1800 due to transmission tunnel and cost half as much again with hardly any if at all performance increase over the 1800S but much less frugal, only advantage was a bigger boot.