OTTAWA -- A British terrorism ringleader was overheard brainstorming attacks just hours after dropping off his houseguest, a Canadian who is now a terrorism suspect, at Heathrow Airport, a court heard yesterday.

On Feb. 22, 2004, Omar Khyam drove his Suzuki Vitara jeep to a friend's house after making sure Mohammad Momin Khawaja got on an Air Canada return flight, ending a three-day visit to Britain.

Mr. Khyam went on to discuss possible plots against British gas, water and electrical systems that night, according to surveillance evidence aired inside Ontario Superior Court yesterday. The trial of Mr. Khawaja, the first person charged under Canada's Anti-Terrorism Act, had previously heard that the Ottawa native stepped into a sophisticated surveillance dragnet when he visited the U.K. suspects. On Monday, the trial is to hear evidence concerning what happened when he returned to Canada.