A former MI5 agent tells us why it’s so easy for terror suspects like Khalid Masood to move around without being arrested

Prime Minister Theresa May has just told the House of Commons that Khalid Masood, the man who carried out the Westminster Bridge attack, was known to MI5 for years but had been dismissed as a “peripheral” figure.

“Some years ago he was once investigated by MI5 in relation to concerns about violent extremism. He was a peripheral figure. The case was historic. He was not part of the current intelligence picture. There was no prior intelligence of his intent or of the plot,” May said.