Romans Estate v. Tassone 2009 BCSC 194 is a very good case authority of the executor that reviews the legal authority of an executor appointed under a valid will.
The matter related to the estate of an elderly man who was stricken late in life and
conveyed assets to a friend and named his new apparently much younger female caregiver his sole beneficiary.
The Court found:
The Executor’s Authority
 Probate in common form is the procedure by which a will is approved by the Court as the last will of a testator. Probate in solemn form pronounces for the validity of the will. It also confirms the appointment of the person named as executor in the will. The Court issues an order, called the “letters probate”, as proof of his or her authority to deal with the estate.
 Executors, however, take their authority not from the letters probate, but from the will itself, and, thus, they may act for the estate from the death of the testator.
 Of course, it may be necessary for an executor to act on behalf of the estate pre-emptively, for example, to preserve assets or to make claims and satisfy limitation periods. That said, the author of Feeney’s Canadian Law of Wills, 4th ed. (Toronto: Butterworths, 2000) at s. 7.33, page 7.13 notes that “[a]s a practical matter, however, there is little executors may do, other than pay debts, until letters are issued to them because the letters, for most purposes, are the only recognizable evidence of their authority”.
ER 991 (Ch. D.), Goulding J. referenced earlier jurisprudence noting that an executor’s authority was based on the will, not on obtaining probate, but obtaining probate was necessary to perfect the action and obtain judgement. Goulding J. held that the court should not, even where the defendant is prepared to admit the executor’s title, waive the production of letters probate:
40] The authorities in my view make several matters clear: (1) an action can be commenced without obtaining probate, as an executor’s authority is based on the will, (2) before proceeding with an action already commenced, the parties to an action may require that the Plaintiff prove their authority by producing letters probate, (3) the court may require that a Plaintiff prove their authority, by producing letters probate, of its own motion, when appropriate and (4) the court may order a stay of proceedings any time after the commencement of an action where it is in the interests of justice to do so, pending the issuance of letters probate.
The law seems to be clear that an executor can bring an action in his or her capacity as executor before probate is granted but cannot obtain judgment in the action without probate having been granted: see Chetdyv. Chetdy,  1 A.C. 603 (P.C.), cited by Allen J. in Harshenin v. Bayoff,  B.C.J. No. 3161 (S.C.).