Eight months after the London train bombings, British police have a lot of information but no suspects—because the Muslim community in Britain is covering up for the plotters: Who Guided London’s Attackers? (Hat tip: Allah.)

In the eight months since Hussain and three other suicide bombers killed 52 people on the transport system here July 7, police have reconstructed parts of the plot in minute detail. They have found that the multiple attack was cheap as well as simple. It cost less than $5,000, said Det. Supt. Peter Wickstead, the chief of an anti-terrorism finance investigation unit, at a recent conference here.

But anti-terrorism officials say the investigations of the bombings and failed follow-up attacks on July 21 have been slow and difficult. Not only are extremist networks murky and fragmented, but investigators also have run into resistance and radicalization on the street: In a recent poll of British Muslims, almost a quarter of respondents said they felt some sympathy with the motives of the subway bombers.

“The absence of hard data on 7/7 is striking,” Shamit Saggar, a political science professor at the University of Sussex, said at the conference at the Royal United Services Institute think tank. “The only way we can explain that is as a significant circle of tacit support existing in that community.”

Three of the four dead bombers were middle-class Britons of Pakistani origin from the northern region of Yorkshire. Investigators suspect that they got help and training from an Al Qaeda network in Pakistan that had targeted Britain before. In contrast, the imprisoned would-be bombers who on July 21 tried to blow up three trains and a bus were East African refugees and ex-convicts based in London.

Despite the timing and similarities, police have found no concrete links between the two groups, anti-terrorism officials said.