Now this information needs to be treated with extreme caution, since the source in my experience is not of the best, but the Spanish newspaper El Mundo is claiming that the Spanish national intelligence centre (CNI) identified a website posting on 29th May from the Abu Hafs al-Masri Brigades which may be seen with the benefit of hindsight as giving clearance for the London attack. If confirmed, this report complicates things slightly since it is not the same group as the “The Secret Organization of al-Qaida in Europe”. The website posting contained the key phrase “We now call on the mujahedeen around the world to launch the expected attack”.
An English version of this story can be found here. I think we should await more confirmation before drawing too many conclusions. Just in case: you can find some background on Abu Hafs al-Masri Brigades here.