Free online training for the public on how to react to a terrorism incident is being made available by police.
The course devised by UK counter-terrorism officers and experts was previously only open to company staff working in crowded places such as shopping centres.
Counter Terrorism Policing is inviting people to take the course and become so-called CT Citizens.
Police said the move was not in response to the London Bridge attack.
But the National Police Chiefs’ Council (NPCC) said the 29 November incident, which left two people dead, was a “stark reminder” of the “ongoing threat and the need for vigilance”.
The training was originally made in partnership with retail giant Marks & Spencer. Called ACT Awareness, it is made up of seven modules and takes 45 minutes to complete.
Deputy Assistant Commissioner Lucy D’Orsi, senior national co-ordinator for protective security at the NPCC, said the course was especially useful for anyone working in or regularly visiting crowded places.
“The threat level remains at substantial, meaning an attack is likely, so giving everyone the chance to be extra eyes and ears for police and local security teams helps to keep all communities safe,” she said.
“The festive period is obviously a very busy one, so this is a good time to join up and become a CT Citizen.”
She said more than 1.5 million modules have been completed to date.
The UK’s terrorism threat level is currently substantial, meaning an attack is likely. The grading was lowered from severe – meaning an attack is highly likely – on 4 November.