MI5 boss Andrew Parker: UK terror threat evolving at scale never seen before

The UK is facing a "multidimensional threat" that is rapidly evolving "at a scale and pace we've not seen before", the director general of MI5 has warned.Andrew Parker said the security service is operating at an unprecedented level and has seen "a dramatic upshift in threats this year".Speaking in central London during a rare public appearance, Mr Parker paid tribute to MI5's 4,000 intelligence officers and the agents who risk their lives operating undercover to protect the country.