They would not be able to talk about a convention per se, in the sense that the traditional view of convention is that you need some precedent as well as discussion in principle. So you need a constitutional principle that is being protected, some statement by the actors that they feel bound by a rule, and some precedent. That's the formula the Supreme Court looked at in 1980.
I think they would carry on and examine the principle involved and any statements from politicians about whether they would feel bound by this in advance. The Prime Minister has quite clearly indicated he would follow this process. That's quite an important statement in setting the foundation for a convention.