Counter-terror police are training thousands of staff in an effort to minimise the risk of attacks at major summer events.
The Summer Security campaign was launched for the first time last year after a flurry of atrocities in London and Manchester.
As millions prepare to attend festivals, concerts and sporting events in the coming months, police have issued a renewed call for workers and members of the public to be on alert for suspicious activity.
The national counter-terror policing network said its experts are working with organisers at major venues around the country to ensure thousands more staff will be able to minimise the chances of attacks and mitigate the impact if incidents do occur.
Officers stressed there is no intelligence to indicate an increased threat to summer events but urged people to familiarise themselves with safety information.
Detective Chief Superintendent Nick Aldworth, the national co-ordinator for the police's protect and prepare strategy, said: "Summer Security is all about making sure people can enjoy themselves safe in the knowledge that the staff around them are trained to know what to do should the worst happen.
"Sadly we have seen that these big public events and crowded spaces can be targeted by those who want to cause harm, but I want to reassure the public that the police, partners and the event organisers are doing all we can to keep them safe and secure.
"You can help make these events safer by reading our Run, Hide, Tell advice, and to be ready to act if you spot suspicious behaviour and activity.
"Don't think you might be wasting our time, it is always better to be safe than sorry. If something doesn't look or feel right, tell someone."
Police advice for people attending events says they should: arrive early for extra security measures; report to police immediately if they spot someone acting suspiciously; never agree to look after anyone else's bags; and listen to announcements if there is an incident.
In the event of an attack, people are advised to run if they can, or if not hide, and then alert authorities only when it is safe to do so.