There's a question being posed on Facebook - one of these "thought you might be interested in this" pages which FB automatically offers.
It asks "if you were locked inside a car and only had a baseball bat, how would you get out?"
Almost everyone has replied by saying "it is impossible to be locked inside a car - just operate the door handle and it will unlock and then open the door". Have they not heard of deadlocks? Are people so out of touch with modern technology that has existed since at least 2008 (the age of my car) and probably for a lot longer.
The whole point of the second deadlock position on a car's central locking is to disable the inside door handles so a thief can't just smash a side window, unlock the door from the inside and (once he's defeated the ignition lock) drive away. OK, he can still wriggle in through the window he's broken but it's a lot harder to do that surreptitiously and you have no quick means of escaping if the police stop the car and you try to leg it on foot.
I know that this is how it works because I accidentally locked my wife in my car when I stopped at a motorway service station for a pee. She stayed in the car and I walked away, automatically pressing the lock button twice as I always do when I'm on my own. When I got back, she was *not* happy because I'd locked her inside with no way of getting out. We tested it later. The system will not allow you to lock the car with the keys inside - it probably waits for the door to be opened from the inside (as the driver gets out of car) before allowing the deadlock to be armed. But it will let you lock someone else in the car if you and your keys are outside.
I've never made that mistake again!