[Stuart]

And they can occur even in the middle of the day, in a safe area. I'm fortunate enough to live in a very safe area (one of the quieter parts of Bromley), and yet during the summer, my neighbour (who does have a habit of opening ALL his windows) went in his living room to find that something had hopped in through the window, while he was pottering round the garden and his wife was in the next room doing something with their son. Thankfully, they only got away with a few small nick nacks (presumably the 50inch LCD bolted to the wall in front of the window would have been too difficult to remove quickly), but they still got burgled.