The national terror threat level has been reduced from critical to severe for the first time since the attempted car bomb attacks on London and Glasgow Airport.
Home Secretary Jacqui Smith announced the reduction in a statement and said there was "no intelligence" to suggest another terrorist attack was imminent.
But Ms Smith underlined that the review did not mean the overall threat had disappeared and urged the public to remain vigilant.
The decision to lower the threat level was made by the Joint Terrorism and Analysis Centre (JTAC), according to the Home Secretary's statement.
She said: "There is no intelligence to suggest that an attack is expected imminently. However, the reduction of the threat level to severe does not mean the overall threat has gone away.
"There remains a serious and real threat against the United Kingdom and I would again ask that the public remain vigilant."
The JTAC had made its decision based on the "very latest intelligence" and had considered various factors including capability, intent and timescale, she added.
The Home Secretary also re-iterated that the threat level to Britain is kept under constant review.
A severe threat level means an attack is highly likely, compared with critical, which indicates an attack is expected imminently.
