MI5 director-general Jonathan Evans briefed the Cabinet today on the terrorist threats facing the UK in the run-up to the London Olympics.
It is thought to be the first time that Mr Evans has addressed a full meeting of Prime Minister David Cameron's top team this Parliament.
But Downing Street officials said it was a "routine" update, and not prompted by any new intelligence or change in the assessment of the terrorism threat level, which remains "substantial".
Home Secretary Theresa May also addressed colleagues on legislative efforts to confront the terrorist threat, including measures in the recent justice and security Green Paper.
Today's 40-minute discussion in Cabinet began with a 15-minute briefing from the Security Service chief, which Mr Cameron's official spokesman characterised as "an overall assessment of the current terrorist threat to the UK".
The spokesman added: "There was some discussion of the Olympics and preparations in that context.
"It was a broad discussion about terrorism and an assessment of the current threat and a run-through of the various issues that the Government is dealing with on the legislative side, such as the fact that we have replaced control orders with TPIMS (Terrorism Prevention and Investigation Measures) and the various measures that are being considered in the context of the security and justice Bill."
The recent spate of killings by a motorbike-riding gunman in south-west France were mentioned but not discussed at any length, said the spokesman.
Mr Evans regularly takes part in meetings of the National Security Council - created by Mr Cameron shortly after the 2010 election to bring together senior ministers, security chiefs and military top brass at 10 Downing Street.
But the PM's spokesman said: "The Prime Minister is keen that some of those discussions that would generally happen at the NSC are occasionally brought to the full Cabinet, so that those Cabinet ministers who are not members of National Security Council are briefed and get an opportunity to discuss the issues."
Cabinet met today in the Large Ministerial Conference Room in the Palace of Westminster, rather than Number 10, as ministers had to get away promptly to attend the address by the Queen to both Houses of Parliament.
The meeting was cut short before the scheduled agenda was completed, in order to ensure ministers were at their seats in Westminster Hall in time for Her Majesty's arrival.