What is the test for "special circumstances" in a limitation period application?

In Deaville v. Boegeman, supra, at pp. 729-30 O.R., MacKinnon A.C.J.O. stated with reference to "special circumstances": A number of courts have made rather heavy weather out of the meaning of "special circumstances" and have sought to establish conditions or detailed guide-lines for the granting of relief after the expiry of the limitation period. This is a discretionary matter where the facts of the individual case are the most important consideration in the exercise of that discretion. While it is true that the discretion is not one that is to be exercised at the will or caprice of the court, it is possible to outline only general guide-lines to cover the myriad of factual situations that may arise.