In London, there is considerable skepticism as to the validity of the latest claims partly because they came on the eve of the government's announcement of a major crackdown on terrorism in the next parliamentary session. But this is not the first time concern has been raised about possible attacks on London's landmark buildings at Canary Wharf. The Docklands estate has three landmark skyscrapers. One tower houses the world headquarters of HSBC bank, the target of terror attacks in Turkey last year. Another houses Citigroup. The Telegraph and Trinity Mirror newspaper groups are also based in the tallest tower, One Canada Square.

Security has been stepped up recently at Canary Wharf with major financial institutions like Citigroup and JP Morgan bringing in new measures to safeguard their staff and their businesses. While skepticism surrounds the veracity of the latest claims, there is, according to security sources, growing evidence that that Britain is being persistently targeted by Al Qaeda agents.

Earlier this year, the highly respected International Institute for Strategic Studies warned that up to 18,000 Al Qaeda terrorists had been deployed all over the world. And Eliza Manningham-Buller, head of MI5, the UK's counter-terrorism agency, has already spoken publicly about Britain's success in thwarting fanatics. Earlier this month, he warned that an Al Qaeda attack on the UK was a distinct possibility. "There is a serious and sustained threat of terrorist attacks against UK interests at home and abroad, " she warned.

The newest reports, if true, mirror this summer's US news of a thwarted plot against major Northeast buildings. The Citicorp building and the New York Stock Exchange in Manhattan; the International Monetary Fund and the World Bank buildings in Washington; and the Prudential building in Newark, NJ were the potential targets of that attack.

In contrast to the skepticism that surrounds the latest report, US Homeland Security Secretary Tom Ridge said at the time that those US threats were more than just the "usual chatter."