One of the top al-Qaida operatives known to have been captured in Britain appeared in court amid heavy security on Monday for sentencing in a plot to bomb the New York Stock Exchange, the International Monetary Fund headquarters in Washington and to use a dirty bomb in London. Dhiren Barot, 34, started plotting in 2000 what he said would be a "memorable black day for the enemies of Islam," prosecutor Edmund Lawson said at the start of what is expected to be a two-day sentencing hearing. Flanked by two court guards, Barot sat expressionless behind a glass wall as the proceedings began. Born in India but reared in Britain, he pleaded guilty last month to conspiring to commit mass murder in terrorist plots on both sides of the Atlantic. He faces a life sentence. The criminal plot was to carry out massive explosions in Britain and in the United States, Lawson said, and was meant to kill "hundreds if not thousands of innocent people without warning." Prosecutors say Barot had planned to cram three limousines with gas cylinders and explosives and detonate them in underground London parking garages and had also identified several London hotels and railway stations as potential targets. Other attacks in Britain included using a dirty bomb and blowing up a petrol tanker, according to Lawson.