Police and MI5 have foiled what would have been the first ISIS terror attack in the UK, it has emerged.

Four men were arrested yesterday morning in connection with terror offences, but the full scale of their plot has only just come to light.

The Times reports that the group are suspected of planning to carry out terror attacks on the streets of London after acquiring weapons for attacks on individuals. Authorities suspected they may even try to carry out copycat beheadings on the capital’s streets, inspired by the videos showing the decapitations of hostages.

Last year, soldier Lee Rigby was murdered by two Islamist extremists who attempted to behead him outside his army barracks in Woolwich, London.

Fear of a home grown attack have increased since the UK joined air strikes against the self-proclaimed Islamic State. In August the terror threat level was raised to ‘severe’, its second highest level, meaning that a terror attack is ‘highly likely’, while earlier this week, Breitbart London reported that anti-terror police activity is at its highest level for nearly ten years.

Counter-terror researcher Olivier Guitta told the Times that the threat of an attack in Britain had risen ten-fold since the UK joined US-led air strikes, adding: “They should be very worried not only of returning jihadists but of people who are here. They will say, ‘I am not going to go all the way to Syria, I can just do it here’.”

At least one of the men arrested has reportedly returned from fighting in Syria.