It's because he has not one, but many, important meetings. He may have to take the last flight out to Frankfurt for an early morning meeting after a full schedule of equally important meetings in London. More time at the airport means less time spent with an extremely important client in London at a meeting when things really start to come together late in the day and staying an extra fifteen minutes could mean clinching a £50m transaction. Traffic is then slightly worse than expected and, hey presto!, you get to the terminal 25 minutes before departure. Most people on business tickets with only hand luggage would quite rightly get very annoyed if they were denied boarding by some brainless jobsworth tapping his watch telling them they are five minutes too late, especially if they later saw that the flight departed 20 minutes late. If, on the other hand, they ran up to the gate to see the doors shut and the aircraft pushing back, they would blame no one but themselves (unless a Prem, in which case they'd expect the plane to come back for them).

BA just make me think of guns and feet at the moment.