Android: Where is the clear all button for my running apps?

On my Android phone running ICS 4.0.4 if you hold the home button, a list of running apps shows up. Here you can return to the apps by tapping them, or close them by swiping them away. Sounds pretty good, but what if I want to close all of them, which I often do since my phone is getting older and slower on a daily basis. Please can we have a "kill all" or "clear all" button added to this screen. I can't be bothered to swipe away 25 open apps, I'm much to important for that. Edit: So it appears as if this list is less of "running apps" but more a "activity list" I was misinformed by this...