They will review contingency plans and risk levels, which might lead to a decision on whether extra resources, such as more staff or CCTV coverage is required.
If a suspicious package were found on the route a safety cordon would have to be implemented. This would effectively stop the event and organisers would need to take into account how this might affect transport links. Planned road closures would need to be re-examined to ensure emergency services could respond quickly.
Organisers will be reviewing the number of security staff in place. They will be revisiting all the key areas on the route, perhaps limiting the number of spectators that can congregate in any area and, if the worst should happen and the event has to close, they will need to assess how best to ensure this is done safely and minimising risk to the public.
Ultimately they will be working under police guidance. Good intelligence and planning is always key.
Eric Alexander is managing director for G4S Events, the UK’s largest provider of security for events.