Khan is one of the leaders of a mosque in the London suburb of Wimbledon. Its green onion domes shine in the afternoon sun in a busy thoroughfare close to the world-famous tennis courts.
Khan says he thinks the attackers were not British. He also says that while extremist Muslim groups may exist in Britain, there are none in his community.
"Well, I don't know," Khan said. "Maybe. Maybe, if the police say so, then they should be there, but we don't know, really. We have no problem really with this mosque at any time. And it's very cordial, friendly. We try to help each other. In fact, tomorrow we have [an] interfaith meeting in this mosque, so it is quite good."
Khan proudly displays the latest issue of the mosque newsletter. "With absolute confidence I say to you, those who commit these atrocities are either insane or bent upon bringing disgrace," one article reads. "In either case, we have nothing [to do] with them, and they have nothing with us."
A few kilometers away, Tahramee is an activist at London's Tooting mosque. He says the extremists could not belong to any "normal" mosque, because they would be quickly excluded.
He includes among "extremists" one of Britain's most controversial militant Muslim organizations, the Al-Mahajiroun, which is tied to London-based cleric Umar Bakri Muhammad. The group advocated the creation of an Islamist state in Britain, and Bakri has asserted in a sermon on the Internet that Islamist attacks in Britain are permissible.
Tahramree calls the Al-Mahajiroun a terrorist association.
"I heard this name, but I think they are nothing but a terrorists association," Tahramree said. "They are totally uneducated people. They are totally brainwashed by the mullahs, and they are telling them to actually do this sort of stuff."
Israel says two alleged members of the Al-Mahajiroun took part in a suicide attack in Tel Aviv in 2003. The group is since said to have disbanded.
Close to the Tooting mosque, a group of teenage Muslim girls walks past slowly. They say they attend the Brentwood state college, and they are returning home from school. They condemn extremists and point out that there were Muslims among the casualties, but they say they do not know of any extremist groups in their community.
"There probably are some here in Britain, but they probably are under cover, you know," one girl said. "They won't, they won't really put, you know...Because in the mosque, you know, we, we condemn violence. We think this is wrong what they are doing."
It seems that an overwhelming majority of British Muslims have no idea where or who the extremists are.
And it seems to be impossible to contact Al-Muhajiroun leader Omar Bakri Mohammed or his deputy, Anjem Choudary, formerly a lecturer at the London School of Shari'a. Calls to their three known numbers produce messages from the telephone company saying the calls cannot be connected.
Another controversial radical cleric, Abu Hamza, is in prison awaiting trial for allegedly soliciting people at religious meetings to murder non-Muslims, including Jews. A handful of his followers have been banned from the Finsbury mosque where Abu Hamza preached.
So are there any extremist groups operating today in Britain?
Inayat Bunglawala is a spokesman of the Muslim Council of Britain -- perhaps the most prominent mainstream Muslim organization in the country. The group's leader recently was knighted by the Queen for working to promote understanding between religions and community and it has strongly condemned the bombings.
Bunglawala says extremists groups are still around but now they have gone underground.
"Al-Muhajiroun officially disbanded last year," Bunglawala said. "But they still exist as remnants. I mean some of them went to this so-called Seydi Effect group. Some of them have re-emerged under different names, go underground, but the elements of hatred are still there."
But could the extremist groups grow stronger in the future, or are they – as many mosque leaders say -- effectively isolated from mainstream British Muslim life by disgust over their tactics?
Dr. Ghayasuddin Siddiqui, the leader of the Muslim Parliament and a director of the Muslim Institute, says there is no formal "ban" in the community on the groups, but they are considered outcasts.
"There is no formal thing [as a ban], but a lot of people have told us that anybody who claims to have any association with Al-Muhajiroun are simply unwanted, undesirable people in any mosque," Siddiqui said.
It seems that the perpetrators of London's carnage cannot really hope for any support from mainstream Muslims.
As London police announced on Sunday, more than 1,700 people so far have phoned their special line with clues related to the bombing. The callers provided "much valuable information," and many of them were Muslims.
Who's Fighting The Real War Against Islam
British Muslims Condemn London Terrorist Attacks But Fear Intimidation