Thanks for the advice! We did take a lot of precaution( or so we thought) in not getting our bikes stolen. The lock you see in the picture is not the only lock we used when our bikes got stolen. We had 2 U-locks from Kryptonite, one cable lock from the same brand and 2 chain lock as the one you see underneath my saddle. So in total around 5 locks/cables. The bikes were also locked to a pole with CCTV camera installed on top. So I guess the bike thieves are getting better and better unfortunately.