13,500 people gathered in London's Trafalgar Square at 6 p.m. Thursday night to sing Hey Jude together. More than 2,000 wireless microphones were passed out and the lyrics projected on a large screen. 24 cameras and recorded the singalong. Here's the 4-minute version -- a T-Mobile commercial.

According to RapidTalent -- a casting agency that can seed a flash mob -- the ad aired "during a specially extended ad break on ITV1's Britain's Got Talent Saturday night." About 200 professional singers were placed in the crowd.