Hamilton R. Leeman (mostly referred to as Mr. Leeman) was a Cabin Pressure character who appeared in Series One's Boston. In the episode Leeman was an angry, argumentative American passenger on MJN Air who was flying from the United Kingdom to Boston.
He gets into conflict with the MJN Air crew (arguing with them all directly except for Douglas), due to him refusing to stop smoking during the flight. He tries to sneak a smoke in the toilet, covering the smoke detector, leading the pilots to very briefly think the plane was on fire.
He is warned about this and dismissively tells them that they didn't really think the plane was really on fire. The crew then tell him that if it happens again they'll assume it is. When it does happen again, Martin sends Arthur into the toilet with a fire extinguisher which he sprays Leeman with which causes him to have a heart attack.