Must be to balance the bonnet. You made an interesting point. My mother told me that when she was little, she and her nanny would travel from their London house to Hendon in a car with chauffeur and footman, followed by another with chauffeur and footman and the luggage. At Hendon they changed to the country cars sent from Northamptonshire to pick them up. Interesting that Hendon was then, in the thirties, considered the edge of London.