Get burgled and uninsured in one step

Sarah Coles
House keys
House keys

/Press Association Images

On the one hand, we're careful to make sure we lock up every time we leave the house, and take security very seriously. On the other, we make a simple and very daft mistake that massively increases our chances of being burgled - and can invalidate our insurance at the same time.

So what is this stupid mistake, and who is most prone to it?