A copper bottomed agreement? - Court of Appeal provides guidance on agreements to agree

It is well established that agreements to agree are unenforceable.

On the other hand, as Lloyd J said in Pagnan SpA v Feed Producers [1987] 2 Lloyd's Rep 60, contracting parties are "masters of their own contractual fate" and "there is no legal obstacle which stands in the way of the parties agreeing to be bound now while deferring important matters to be agreed later".

Where, then, is the dividing line between an unenforceable agreement to agree and a contract which binds the parties, despite leaving some issues for future agreement? Guidance can be found in the recent case of MRI Trading AG v Erdenet Mining Corp LLC [2013] EWCA Civ 156.