As well as the London Bombing related spam I reported which arrived within 24 hours of the bombing, there is now a London Bombing computer virus being reported by the BBC andourselves. More specifically this is a trojan and not a virus, but it is still an unpleasant program you don't want. This arrives in the form of an email claiming to be from CNN offering video footage of the bombings. If the attachment is run under MS Windows, it may place your computer under someone else's control. Since this has now been discovered, it is likely that the author may re-write the program to disguise itself differently.
It is good general practice to never open attachments you weren't expecting, and to use an up-to-date anti-virus system and firewall.