It is a rather strange topic, and I doubt Mycroft was keen on mentioning anything about Cordona. The fact that you even know a little of it at all is...

[ He shakes his head. He's told his Watson some stories about Cordona, mostly related to cases, but there are things he has yet to say. ]

My Watson has yet to meet Mycroft, and if I could spare him the tedium and how utterly vexing he can be, I would. Did he ask you to do something for him? Something for Queen and country but keeping you in the dark all the same?