I spotted a blog post named Catching Terrorists with Google Adwords via DigitalPoint Forums and then tested to make sure it is real.
Do a Google search at the UK engine on hydrogen peroxide, and up comes an ad that reads, "Hydrogen Peroxide - www.met.police.uk Suspect it? Report it. Call the Anti-terrorist Hotline." Here is a screen capture:
Clicking on the ad takes you to the Metropolitan Police Anti-Terrorist Hotline page. The page says, "If you suspect it, report it."
Found that very interesting.
Forum discussion at DigitalPoint Forums.