Are you left, right or down the centre-line…?

A British Airways 737 touched down at Frankfurt-am-Main. The tower controller, obviously in frivolous mood, transmitted: "Speedbird 123. Nice landing Captain, But a little left of the centre-line, I think." Quick as a flash, the BA Captain replied in a cool English accent: "Roger Frankfurt Tower. Perfectly correct. I am a little to the left of the centre-line. And my co-pilot is a little to the right of it."