AN AL-QAEDA plot to target GCHQ was last night suggested as the possible trigger for the arrest of a suspected terror agent in Gloucester. GCHQ - the Government Communications Headquarters - has been at the centre of the fight against terrorism, providing vital intelligence to authorities, particularly in the wake of the 11 September atrocities. GCHQ’s Cheltenham offices, which are about ten miles from yesterday’s first arrest, were created to streamline the task of monitoring countless phone calls and e-mails around the world to aid the fight against terrorists. Housed in an elaborate circular building, Britain’s £1.6 billion spying centre...