Had a chat with my dad at the weekend and he remembers the occasion. It was him and David you met. Regarding the "twice the wheel height" he has given me the following, his memory from discussing it with Ian Cameron:
"Ian Cameron, designer of the BMW/Rolls-Royce Phantom, described in a lecture the philosophy that led to the car's design. To capture the essence that a Rolls-Royce should portray he imagined a rich and famous owner who, of course, had a very beautiful wife. The car would present her to an important “red carpet” Gala occasion. She would alight to a throng of photographers each eager to get a shot of elegant leg! (my words, not Cameron's). So she is in control of the resulting images, when she steps out her head must emerge first and she must step down. The height of the car floor is thus determined by an initial step down in the car with a further step down to the carpet. The picture is framed by the car and a liveried chauffeur who opens the door but must then step back out of focus. So the door has to be rear hinge (Aprilia/Aurelia). The car is the backdrop so must be beautifully proportioned and under stated to project the owners impeccable taste. The floor height determines the roof height which in turn determines the wheel diameter which should be half the height of the roof. The Phantom has, thus, very large wheels for which special tyres had to be procured. The rest of the design then follows.
In conversation afterwards my ownership of a B20 was mentioned which excited Cameron's interest. When asked why he said he had worked at Pininfarina and it was one of the house icons. The picture illustrates why!
As in so many other features, Lancia's designs were so far ahead of the “herd” that they rarely get the credit they are due."