London, Apr. 1 : It is glorified house arrest here. No less. For those who need to commute to work to downtown London on the first or the second, it is going to be a harrowing exercise.

Everybody has been advised to carry as many forms of identification as they possess. Roads are blocked, thousands of policemen are patrolling the streets, presidential cavalcades are speeding down roads, potential protest demonstration sites are being sanitized for public movement, banks and governmet institutions are being guarded with particular emphasis

At the Excel centre, where the meetings between G-20 leaders will take place, the security is so difficult that residents living in the area might as well not step out.

The Dockland Railway Station will be closed near the centre. The security exercise is the most complex and vast one ever undertaken by the Scotland Yard. And the most expensive one too. The guesstimates are about 7.5 million pounds for the two day summit.

Already there is a severe level of alert, which means that offials believe that an attack is highly likely. What or who could be the target is anybody''s guess. The most protected man of course is US President Barack Obama.

Travelling with the President are over 200 Secret Service personnel who protect him round the clock. The US First Lady has her own guards. Obama has also flown in his armour plated limousine known as "The Beast".

Other more lowly heads of state of rich nations have strict security measures in place, but ofcourse, none can match up to the US President''s security apparatus.

It''s not only the dignitaries whose security is causing a worry. Also under threat are banks and luxury hotels. After the Mumbai attacks, hotels in London have carried out security drills, installed CCTVs and are cooperating with the Met Police department reporting any suspicous activity.

About 5,000 police are stationed across Central London, and an additional 35,000 policemen are on standby for the summit on Thursday. They will mainly fan out in the Docks region where the summit is being held and the financial district. Following November''s seaborne attack on Mumbai, extra patrol boats will guard the steel gray waters of the River Thames, and police frogmen will scour the river''s length for floating bombs.

Some leaflets were found last week urging protestors and demonstrators to "Bash a Banker" or "Storm the Banks". Consequently, banks have increased security and have conducted drills to evacuate and seal their premises in the event of a protest demonstration turning violent in their premises. Some banks will only have their essential staff coming in for duty on the first and second in the downtown areas. Multinational companies have cancelled all conferrences for the entire week.

Terror groups could also use the garb of being regular protestors and mount attacks.

Protesters have threatened to train their anger on the city''s financial center, urging demonstrators to "Bash A Banker" and "Storm The Banks" in leaflets promoting their rallies.

Banks and hotels have prepared for attempted raids or sieges on their buildings, said Pepe Egger, a senior security analyst at London''s Exclusive Analysis Ltd.

Concern is particularly high because the last major summit in Britain - the Group of Eight meeting in July 2005 - was marked by deadly suicide attacks on London''s transit network that killed 52 people.

Tens of thousands of demonstrators are planning to stage four days of protests at sites across London, threatening to overwhelm police and potentially leave the British capital more vulnerable.

British Home Secretary, Jacqui Smith, said that while no specific plot against the G-20 summit had been identified, terrorists could strike "without warning at any time."

Michael Clarke, the head of London''s Royal United Services Institute think-tank, said small terrorist groups may use the cover of planned protests by environmentalists, anti-war protesters and labor unions to mount an attack. (ANI)