The 'third and final command post' security exercise is taking place over the next few days in advance of the London Olympics 2012, bbc.co.uk reports.
The three-day test commences on Tuesday 24th March and it will involve 4,000 government officials, games organisers, representatives from the emergency services, council workers and transport operators across the country.
The security test will simulate the busiest three days of the Games, August 4th - 6th; during which time, 26 sporting events will be taking place at 14 separate venues. These include tennis at Wimbledon, the triathlon in Hyde Park and beach volleyball at Horse Guards House.
'Random incidents' will be staged to monitor reactions and resolve any issues, lbc.co.uk reports. It will specifically test resilience, decision-making capabilities - as well as the effectiveness of the main communication, command and control processes that are currently in place.
This is the last such security test which will be held, but it should give spectators confidence that every eventuality has been considered.
Commenting ahead of the test, culture secretary Jeremy Hunt said: "Obviously nothing can fully prepare us for the reality of hosting the world's biggest sporting event, but we really want to make sure we do all we can to ensure we deliver an Olympics and Paralympics that are as safe and secure as possible, while also making sure everyone involved has a great time."