A Union flag flies near the Elizabeth Tower, better known as ‘Big Ben’, and the Houses of Parliament in central London on March 6.LONDON, March 6, (AFP): Security services have foiled 13 potential terror attacks in Britain since 2013, its most senior counter- terrorism policeman said Monday, with more than 500 active investigations at any one time. Mark Rowley, assistant commissioner of London’s Metropolitan Police, said incidents inspired by the Islamic State group were a “large part” of the problem although al-Qaeda remained a significant threat, while the far-right was also an issue.