Police in Britain and Italy questioned 21 suspects as they sought to piece together the networks behind the London bombings, probing for possible links between the two sets of attacks and for connections to any accomplices overseas. Investigators arrested seven people Sunday at a four-story brick apartment building in Brighton, on England’s southern coast, and also searched another home in the city. They gave few details about what role the six men and seven women were suspected of playing in the failed July 21 attacks on the catacking three London Underground trains and a red double-decker bus. Full Story