I did London - Delhi - Hong Kong with Jet. My transit time was several hours, but I'm pretty sure I had to go through a security check again even though we stayed in the same terminal. The line for the security check was painfully slow. Maybe you can get to the front. I do remember that the single female security guard got fed up (maybe because she had no break) and then walked off. This meant all the female passengers stopped being processed for half an hour or so.