The UK’s National Counter Terrorism Security Office (NACTSO) issued advice for security managers of crowded places on 26th May, following a change in the UK’s threat level from international terrorism to critical (the highest level) on 23rd May.

The threat level was raised as security services investigated the bomb attack at the Arena concert hall in Manchester on 22nd May.

On 27th May the threat level was reduced from critical to severe, but Prime Minister Theresa May emphasised that a threat level of severe means an attack is “highly likely” and “the country should remain vigilant”.

NACTSO’s advice can be found at

It explains the significance of the six different threat levels, critical, severe, substantial, moderate and low, and of the three different response levels, exceptional, heightened and normal.

It suggests some simple, practical actions that can be taken immediately to help improve a venue’s security.

“The security measures deployed at different response levels should not be made public,” it says, “to avoid informing terrorists about what we know and what we are doing about it.”

Actions NACTSO recommends include:

Risk Assessment.

Review response level for sites.

Brief staff to proactively engage with the public.

Build unpredictability into security measures.

‘Recruit’ staff to be vigilant for and immediately report suspicious activity and items.

Review Evacuation, Invacuation and Lockdown procedures. Designate marshals to support the activity.

Identify ‘protected spaces’

Review Emergency Assembly Point

Review First Aid kits’ availability.

Ensure crisis incident kits (grab bags) are available and up to date.

Provide prior notification to staff and visitors of enhanced security measures, encouraging them to arrive in plenty of time and to bring minimal possessions.

Monitor news and media channels

Develop pre-scripted messaging and alerts and communication channels.

Review personnel lists, shifts, leave and protective equipment.

The advice contains further detailed check lists of actions to be taken under the following headings:  TRAINING, STAFF VIGILANCE, PHYSICAL SECURITY, SEARCH AND SCREENING, SECURITY PERSONNEL and GOOD HOUSEKEEPING.