No, certain flights are exempt (you could have searched, multiple posts about this here), the flights are chosen daily, but for instance not all London flights are.

Most people still go through their transit security, which is a mess, with long lines and probably the least thorough checks ever. It's only fairly recently that they started demanding people take out their laptops. Our moderator here claims they have some super sophisticated secret security system (I'm sure they also claim to have one), but I'm not buying it. In a way, it's kind of worrying, but then again...