After the terror attack in Westminster that left four people dead, anxiety among Londoners and city-dwellers around the world is inevitably running high.

Police have arrested eight people after a black-clad man, armed with knives, mowed his car through a crowd of people on Westminster Bridge before stabbing a police officer in the courtyard outside Parliament.

He was shot dead by colleagues of PC Keith Palmer, who died of his stab wounds.

But while the terror threat level remains at “severe” in Britain, it is important to remember the chances of ever being caught up in a terrorist attack are extremely unlikely.

If you do ever witness at attack, police have issued advice about what to do.

First, run to safety if you can. Do not try to surrender or negotiate.

If escaping is not an option, try to hide. This is better than confrontation. Turn your phone to silent and make sure vibrate is also off. If at all possible, barricade yourself in.

Police have issued advice on what to do in the event of a weapons attack (NPCC)

When safe to do so, tell the police by calling 999 if in the UK, and if possible, warn others to stay away.

If you witness or have any information about suspicious behaviour, you can report it in confidence by calling the police on 0800 789 321 or completing an online form.

Police define suspect activity as “anything that seems out of place, unusual or just doesn’t seem to fit in with everyday life”.

Westminster attack: How the day unfolded

Examples include anyone hiring large vehicles for no obvious reason, anyone randomly buying large amounts of chemicals, or anyone taking photos of security arrangements.