An email from a friend in London in the PR business who (I know from personal experience) generally has some great connections shares what people on his end are talking about:
I managed to get into the office before things got bad. I normally cycle into the office but I got the tube this morning which is a little terrifying with hindsight.
The attacks look pretty bad and everyone is calling round checking that friends and family are all OK. The whole tube network is down as are many of the phone lines, much of London has been closed off and the police are warning everyone to stay where they are. Inside sources say that they there may be more attacks planned for this afternoon.