What is the duty of a guarantor to disclose during the term of a guarantee?

In the case at bar, it is necessary to distinguish between the duty to disclose at the time the guarantee was entered into and the duty to disclose during the term of the guarantee. In Toronto-Dominion Bank v. Rooke and Rodenbush, supra, Esson J.A. noted this distinction: The principle to be applied is the same but, generally speaking, it is more likely that a duty to disclose will arise in relation to a variation during the term of the guarantee. In those circumstances, it is likely that a relationship will have been established between the creditor, the lender and the guarantor which will create a basis for finding reliance by the guarantor upon the lender in relation to the business. Another circumstance which is likely to have the same effect is where the guarantors, as in this case, have been customers of the bank for many years before the transaction arose with the particular debtor. Such considerations will, of course, generally apply only where, as in this case, the guarantors were not actively involved in the conduct of the debtor's business. In the common situation in which the guarantor is an active principal of the debtor company there will not often be a factual situation giving rise to an obligation to disclose. (at p.175)