I have not ever thought a great deal about these until a couple of years ago when I was visiting a tribunal office some miles away.  I was collecting boxes of legal bundles for a case.   The security guard on the back door of the court was not at all helpful – he begrudged having to leave the warm reception to come and help lift the boxes into my car.   Anyway just as he was loading the last, and all the doors and boot had been open for along time.  Having secuired the last box, he then went and shut all the car doors for me, then before I could get in, he slammed shut the boot. . .  my car then locked itself as a safety feature – sadly my handbag was on the front passenger seat and the car keys were sat on the driver’s seat!  Panic central. . . . .  I had to ring my breakdown service and they came out to release my car.  The reason I mention this here is that a front door key was also on the fob – if I’d not got in to the car, my house key would have been lost to me also.  That has always taught me to keep the car keys in my hand or coat pocket at all times when loading a car!