The change in the threat level to substantial, meaning an attack is a strong possibility, does not mean the overall threat has gone away—there remains a real and serious threat against the United Kingdom and we would ask that the public remain vigilant. Substantial continues to indicate a high level of threat and that an attack might well occur without further warning.
The decision to change the threat level is taken by JTAC independently of Ministers and is based on the very latest intelligence, considering factors such as current capability, intent and timescale.
As substantial continues to represent a high level of threat there have been no significant change to policing arrangements, and security procedures at airports and other public places remain in place.
The threat level is kept under constant review and can change—up or down—at any time in the future. Short-term changes in the threat level are therefore not a sound basis for making long-term strategic decisions about resourcing.