In Ontario, this situation is covered under Rules 75.02 and 75.06 of RULES OF CIVIL PROCEDURE – R.R.O. 1990, Reg. 194.
An application must be made to court to “prove the Will” that was lost.
If everyone who has a financial interest in the estate agrees to accept the contents of the “lost will” as the intended last will and testament of the deceased then the court will likely rely on affidavit evidence only. If there is no consensus amongst those with financial interests in the estate, then the person who wishes to “prove the Will” must bring an application to court and ask for directions. In this instance, affidavit evidence will be insufficient.
It is important to remember that the courts assume that if the testator had possession of the “lost Will” and no one can find it then unless there is proof to the contrary the court will presume that the Testator revoked or destroyed the will.