Of course it has a practical purpose - butting enemies in the stomach and killing them stone dead. Very useful for getting rid of unwanted archbishops.
Harry: You see, Archbishop Godfrey was coming out of the Duke of Winchester's room--
Edmund: ...who had just died, leaving all his lands to the Church?
Harry: Well, as a matter of fact, yes.
Edmund: And so the King was really after his blood, presumably.
Harry: Well, I dare say, but the point of the matter is that, at that moment, round the corner, came Sir Mortimer.
Edmund: The King's hired killer...
Harry: - No, no, no. Mortimer: that tall, rather striking fellow with no ears.
Edmund: Yes, that's him.
Harry: Well, he saw the Archbishop and rushed towards him with his head bowed, in order to receive his blessing, and, er, unfortunately, killed him stone dead.
Edmund: How?
Harry: Mortimer was wearing a Turkish helmet.
Edmund: Oh, I see, yes: one of those with the two feet spike coming out of the top?
Harry: It's one of those things they normally use for butting their enemies in the stomach and (Edmund joins in) killing them stone dead.