UK home to up to 25.000 Islamist extremists who could pose threat, EU official warns
Number is the highest known figure in Europe, amid concern over "known" extremists launching recent attacks
Buckingham Palace knifeman being questioned by counter-terror police after injuring two officers
Europe is on high alert following a spate of recent terror attacks
Self-driving lorries to be tested on UK motorways
Up to three wirelessly connected HGVs will travel in convoy, with acceleration and braking controlled by the lead vehicle
