Diddle E. Squat:
Or a combination of 2 or all 3. Don't forget that a couple of years ago IRA members were training with Muslim terrorists in S. America rebel camps.
I've an inkling that the Islamo-fascists got help somewhere along the way from the Hiberno-fascists, after all who knows more about terrorist attacks in London than the IRA, too early to speculate, though.
If it was the provos, or whatever it is they are calling themselves these days it'll be totally obvious to the ATS.
That seems incredibly unlikely though. No warnings, sequenced attacks. Like they were setting out to copy Madrid. I think the culprits are pretty obvious. I would also be very willing to guess that we'll hear in a few days or at most a couple of weeks, that they are caught or SAS'd.