Our team sometimes has one-on-one or 3 attendee meetings in of the developers' cubes. We have one developer who always jumps in to "offer" his suggestions for projects that do not concern him. Engaging him tends to derail the efficient nature of our semi-formal/quick meetings, where 1 or 2 developers convene, make a decision, and go our separate ways.
The ad-hoc nature of our meetings doesn't require us to reserve a conference room every time. So meeting in one of our cubes just makes sense.
Comments are always welcome but not necessarily if we are pressed for time and have a very focused agenda for a meeting that does not concern him.
Is there a professional/tactful way to communicate that his behaviour is intrusive and not always welcome?