Al Queda may or may not be responsible for this attack but one can easily make out that this attack is in retaliation to what US and UK have done in Iraq and Afganistan. I offer condolenses to the people killed in London as well as those killed in Iraq. These are the actions of a few crooks sitting in the position of power with their policy to hold onto power as long as they can. Ultimately they are not the ones who pay the price. This price is being paid by the people who are fighting on both the sides. I feel the worst thing these leader are doing is when they call these acts as "Islamic Extremism". Associating these terrorists with the religion which followed by more that 1.3 billion people all around the worlds is only going to create more hatred in muslims as well as non-muslims and divide the world. The terrorist don't follow any religion because no religion preaches you to kill innoscent people.
