Islamic State (ISIS) fanatics have said they will kill hundreds of Britons in Doomsday-style attack that will eclipse the carnage in Paris last year.
It said that the UK is due the “lion’s share” of ISIS’s wrath – in revenge for the RAF’s bombing campaign in Iraq and Syria.
The jihadis are thought to have their sights set on central London, after a recent video highlighted a string of potential targets.
They include Buckingham Palace, Trafalgar Square, Tower Bridge and Big Ben.
It marks a change in focus from the Paris massacre, where gunmen shunned national monuments in favour of restaurants, bars and a music venue.
The ISIS message compared the coming strike to scenes of Armageddon in the Koran.
The whole passage says: “There will be shackles, and fire, and food that chokes, and painful punishments.
“On that day the Earth will convulse and the mountains will become a heap of pouring sand.”
It continues: “How can you defend yourselves, if you don’t believe, from a day that will turn children’s hair to white?
“That day the heavens will shatter. His promise is always fulfilled.”
The 17-minute film features some of the Paris attackers threatening Europe before they set out on their attacks.
One, Abdelhamid Abaaoud, warned that sleeper cells are lying in wait around terror targets.
MI5 and the police are in a constant battle with UK-based terror cells to prevent the next attack.
Their activities are shrouded in secrecy, but the Prime Minister has said at least seven credible attacks were foiled last year.
There are particular fears surrounding the hundreds of ISIS soldiers known to have come to the UK after fighting in Syria.