Originally Posted by 
4bee
				 
			
Our ford T had the tank under the driver's seat - with fuel rationing and a nearly empty tank, proceeding up steep hills in reverse was not unusual. Refuelling required removing the front seat cushion and the board underneath it.  The Reo that replaced it had the tank behind the dash - no problems, small hatch just in front of the windscreen provided access.  No fuel gauges, and you had to turn the fuel off after stopping in case the needle valve leaked and flooded the carburettor, potentially draining the tank.
The Swift we had after that had a rear mounted tank, under the spare wheel, where a boot would be if it had one (there was a folding luggage rack behind the tank). It had a vacuum tank to supply fuel to the engine. The mechanical fuel gauge was on top of the tank.
The Austin that replaced the Swift had a tank under the boot, with a filler in the mudguard, and a fuel gauge in the dash. 
None of these had any sort of lock on the fuel cap. And although the Ford and Reo had ignition keys, they had no door locks - in fact, the ford (a light truck) had no doors. The Swift had a door lock (for which we had no key) but the (factory) ignition was a pushpull switch. The Austin was the first car we had that locked.