The UK has upgraded to serious attacks due to attacks happening in Europe. The attacks happened in both France and Austria on Monday night.
The decision by the independent Joint Terrorism Analysis Centre (Jtac) means the terror risk in the UK is back at its second-highest level,
France experienced attacks when a teacher was killed after he had shown cartoons of the prophet Muhammad to pupils.
Monday's night attack in the Austrian capital has shocked the residents. There were five people, including an attacker who died in a country not known for violence.
Last month, MI5‘s new director-general, Ken McCallum, said the security service had disrupted “27 late-stage terrorist attack plots in Great Britain” of which the majority were Islamist extremists.
Jtac is based within MI5 but operates independently of it and ministers. Its membership is composed of all the intelligence agencies who take a view on the threat to the UK from all forms of terror