PM Theresa May announces Operation Temperer has been enacted - allowing police to call on immediate help of 5,000 troops. UK terror threat level raised from severe to critical, which means further attack may be imminent

The threat level has been raised to critical by MI5's Counter-Terrorism Analysis Centre.

This means that security arrangements known as Temperer come into play, whereby the army take over from the police in guarding and protecting sensitive places, freeing up the police to be more visible and active on the streets.

Assistant Commissioner Mark Rowley, Head of National Counter Terrorism Policing:

24 hours in we have a number of investigative leads that we are pursuing to manage the ongoing threat.

We are flexing our resources to increase police presence at key sites, such as transport and other crowded places and we are reviewing key events over the coming weeks. 

This is part of an agreed and well -rehearsed plan and military personnel will remain under the command and control of the police service.

in Nov 2015 David Cameron delivered a statement on the Government's security and defence review to MPs, having visited the Bataclan theatre in Paris where 89 gig-goers were slaughtered by Islamic State (ISIS) terrorists. "should a similar attack take place in the UK, a new operation had been drawn up to allow thousands of troops to protect Britons."

The plan, codenamed Operation Temperer, would see troops guard key targets alongside armed police officers, providing ‘protective security’ against further attacks while counter-terror experts and MI5 officers hunted down the plotters.

The dailymail has got hold of documents accidentlally uploaded in 2015 to the National Police Chiefs Council (NPCC) website, gives details of what was discussed in a closed session. Soon after, the documents where removed.

It disclosed, after this year’s Paris massacres, senior police officers discussed raising the terror threat level in Britain from ‘severe’ to the highest level of ‘critical’, meaning a terror attack is ‘imminent’ rather than ‘highly likely’.

Intimidating: Surface-to-air missiles in a public park for the 2012 London Olympics

Will Riches, vice-chairman of the Police Federation of England and Wales, said: ‘The bottom line is you can’t reduce 17,000 police officers and expect nothing to change. While police are well-versed at contingency planning, the levels of cuts to officers means that we cannot police events in the same way.’

Baroness Jones, who sits on London’s Police and Crime Committee, said she was ‘shocked’ at the plans, saying: ‘This would be unprecedented on mainland Britain.’ And she expressed concern that the troops would not be sufficiently trained to protect civil liberties.

Some police leaders fear that the soldiers would be needed if there was a wave of attacks by extremists inspired by Islamic State ISIS or Al-Qaeda, as police forces no longer have enough manpower to cope.

GHCQ's Tempora will monitor internet communications terrorists might be using.

This is how the #Manchester attack unfolded https://t.co/j8d3giasxH pic.twitter.com/8NjKMg8O4L

— BBC News (UK) (@BBCNews) May 23, 2017