Yesterday, the government approved a third runway for Heathrow. That means tomorrow (Saturday) is the 'Decision Day' Flash Mob at Heathrow Terminal 5.
If you want to show that you're against unsustainable aviation expansion head along to the 'Security North' section of the terminal's Departures area just before 12 noon. The idea of a flashmob is that it appears out of nowhere, so the plan is to wear a (concealed) red t-shirt, and then on the stroke of midday join the other flashmobbers in revealing your opposition to the third runway.
See you there!