"I have heard conflicting stories about the fingerprint of the explosives used in each attack."
From the info I've been able to gather from reports within the US, the explosive used was triacetone triperoxide (TATP), known to radical Islamists as "Mother of Satan." I've only seen one conflicting report that said it was actually a somewhat similar compound, hexamethylene diamine triperoxide (HMDT). Both are "cooked" from materials that are fairly easily purchased at retail.
Has any link been found between the 7/7 and 7/21 bombers?As I understand it the short answer is 'no'. The thinking is of independent cells that are unaware of each other. I have heard conflicting stories about the fingerprint of the explosives used in each attack. Clearly in the background.... strings are being pulled but mapping that is very difficult.
My toughts too. It means the command and control infrastructure is very likely to be still out there. Probably long scattered by now but sooner or later, likely to rear its ugly head again.
I have to give Brit intel where credit is due tho... hopfully, they are in another discreet "watch and learn" phase of the counter terror operations.