Can a mortgagee set up title as if he had purchased the land as if a stranger?

In Kelly v. Macklem, supra, it was held on the facts of the case that the mortgagee had asked to be allowed to purchase at a tax sale on the ground of his having an interest in the land and could not therefore set up the title so obtained against the mortgagor’s right to redeem. Spragge, V.C. said at p. 30: A mortgagee may purchase as any stranger may; and may say that being a mortgagee shall not place him in a worse position than he would| be in if he were not mortgagee, because he is not a trustee for, and owes no duty to the mortgagor; but if he purchases as mortgagee; makes his interest in the land a ground for being allowed to purchase, can he afterwards set up his right to hold, as if he had purchased, as a stranger?