They announced on the radio that it might have been a hoax
It appears an airport security person in London may have claimed the passenger was suspicious to get back at him. According to the radio report, the passenger gave the airport guard a hard time. If true, not only does the guard deserve to be fired, he/she should be fined for the cost of the fighter escort. Canada uses CF-18s that cost somewhere around $4000 (US) an hour to operate. I suspect the US either used F-15s (~$5000 to $6000 an hour) or F-16s (~$4000 an hour). Hit the jackass where it hurts and you can be pretty sure that kind of thing won't happen again.