Interesting that in BMC's usual methods of saving money by using the Austin 1800 doors on the 3 Litre and Maxi (and the Aussie Kimberley), they elected to put opening quarter vents on the production 3 Litre. I assume this was to make it more 'important', but they never used them on the up-market Wolseley versions. The 1800 was one of the earlier cars to do away with them, and with the ventilating system and opening rear quarters, were up to the job in hot Australian summers. The passenger vent tube goes near the radiator, so a blast of hot air (and leaves) are to be expected for the first few minutes after opening them. The sketch is of the pre-production 3 Litre.