It turns out Harvey was finishing up with BBC Breakfast and needed to get to an interview with Radio 5 Live, according to the Evening Standard. He could tell he was no longer needed where he was and bolted. It starts off a bit sly. He keeps looking at Wright as he steps to his left, out of frame.
Ultimately, he could have pulled it off if it wasn't for the cameraman, who slides just a bit to the right as Harvey leaves the interview. Then the shot moves into a perfect framing of Harvey's dead spring down the track to his next interview.
It may look like a scene from a Christopher Guest movie, but no judgments. We already know that the Irish exit is a sign of high moral character.