Manchester attack: UK moved from severe to critical alert

The UK has been moved to critical alert, the highest terrorist ranking it can face.

As the prime minister explained, that means a further post-Manchester attack may be imminent, in the view of security and police experts.

Daily Politics presenter Andrew Neil explains what moving from the severe, to critical, level means.

More: Follow @daily_politics on Twitter, external and like us on Facebook, external and watch a recent clip and watch full programmes on iPlayer