Whilst we were in Calis last week a large detached villa near to us (a few doors away from the Aydin Pide Restaurant) was broken into and their safe was physically removed. Although they had security bars fitted to all the windows, the thieves managed to get in by bending the bars down far enough from the top to allow a small person (perhaps a child) to squeeze through and open the front door.
The reason I'm posting this is to warn you that it was the design of their security bars that was at fault. There was a horizontal restraining bar but this was about 18 inches away from the top which when the vertical bars were bent down provided a big enough gap to get someone through. The owners have now replaced them with ones which have an additional horizontal bar set about four inches from the top to prevent this type of access. Take a look at yours - they may not be as secure as you think.
SteveJ