Two high-level conferences are being held - the first within the next few days - after intelligence sources suggested the next terrorist attack may be out of London.
It has also emerged that Scotland Yard has film of terrorists parking the lorry which contained the bomb that devastated London's Docklands on Friday.
However, it is understood that the images from surveillance cameras are extremely poor. Detectives hope to obtain better pictures from hundreds of hours of film that have yet to be examined.
Following a series of warnings from police chiefs that a second terrorist attack could happen "anytime, anywhere", two meetings to discuss improved security have been arranged.
A seminar, including chief constables and members of the Metropolitan Police's Diplomatic Protection Group, is due to take place in a few weeks time to discuss greater security for the Royal Family.
In the next few days, a small number of high-level police chiefs, MI5 officers and members of the Home Office will meet in London to draw up new national measures.
They are expected to consider warnings that it is not just London that is in danger from possible terrorist attacks. This follows information from intelligence sources suggesting provincial cities, where security is often more low key, are likely targets.
Regional police chiefs are expected to be urged to develop local strategies for maintaining security at the highest level. A warning of the risks faced by politicians and public figures is also likely.
John Evans, chairman of the Association of Chief Police Officer's Terrorism Committee, said: "Chief constables will be meeting to co-ordinate their response and to check every possible measure is being taken to ensure public safety."
Meanwhile, security in London continued to be tightened and an investigation is underway after two bullets were found close to the home of Baroness Thatcher in Belgravia, west London.
The bullets, discovered on Monday afternoon, are undergoing forensic tests. However, it is understood that Scotland Yard's anti- terrorist squad has ruled out any links between the bullets and an IRA hit squad.
It also emerged that reservoirs in north London and close to Heathrow Airport have been closed after requests from anti-terrorist officers who fear the land may be used to launch an attack or store weapons.
Yesterday, officers and forensic experts continued their search of the South Quay area, scene of Friday's attack. They will now study a number of clues, including pieces of the truck used to carry the bomb.
In Manchester the bomb squad carried out two controlled explosions following a false alarm over a van with Irish number plates at the city's Piccadilly Station.
n The inquest into the two victims of the IRA attack last Friday was opened and adjourned yesterday. Inan Ul-Haq Bashir, 29, from Streatham, south London, and John Jefferies, 31, from Bromley, Kent, died instantly when the bomb exploded and destroyed the shop where they worked.
Both were identified by their fingerprints and from documents found on Mr Bashir.Reuse content