ARMED anti-terror police were flooding London today amid fears a BOMB found on a Tube train last night was just the first of many. Officers tasered and arrested a 19-year-old man after a "viable improvised explosive device" was found on a Tube train at North Greenwich. North Greenwich tube station was evacuated for nearly seven hours after London Underground staff found the suspect package on an eastbound Jubilee Line train. But experts warned the IED may have been just the first in a co-ordinated attack on the capital.