>>>>>>I get a bit marked when I hear a session get hijacked by someone who just wants to show off.<<<<<<<

Spot on, Dave, but it doesn't just happen in Irish sessions. I have been known to speak up on odd occasions as you can imagine. Even worse when it's a mixed session and there are relative beginners trying to get to grips. To compound things this one I'm thinking of used to arrive late at session and then play all the tunes that had already been played at normal speed, at twice the speed.