David Cameron condemned the “barbaric” shootings as he prepared for a “full intelligence briefing”.
The Prime Minister said: “The murders in Paris are sickening. We stand with the French people in the fight against terror and defending the freedom of the press.”
Home Secretary Theresa May will chair a meeting of the Government’s Cobra emergency contingencies committee today to discuss the terror threat to Britain.
Security sources acknowledge that atrocities such as the French massacre and the London murder of soldier Lee Rigby are extremely difficult to prevent.
But even small-scale terrorist operations need planning and the communications between suspects can be monitored.