Some lunatic (I had thought) had been posting stuff on my forum about rushing out to buy your gas masks. However Rueters have reported that 1,000 people have bought gas masks. This seems a tad premature to me. Yes, be vigilant, yes, watch out for unattended packages and bags, but gas masks, sounds like hysteria. Anyone who doesn't normally travel on the tube think about this. Over three million people commute on the London Underground everyday and only 1,000 people(reportedly) have bought gas masks.
(By the way gasmaskshop.com from which I borrowed the picture above has had only 1,342 visitors) Don't act like victims, just be vigilant at the moment.