(1) Where a testator, during his lifetime, has made permanent provision for his spouse, whether under contract or otherwise, all property which is the subject of such provision (other than periodical payments made for her maintenance during his lifetime) shall be taken as being given in or towards satisfaction of the share as a legal right of the surviving spouse.

(2) The value of the property shall be reckoned as at the date of the making of the provision.

(3) If the value of the property is equal to or greater than the share of the spouse as a legal right, the spouse shall not be entitled to take any share as a legal right.

(4) If the value of the property is less than the share of the spouse as a legal right, the spouse shall be entitled to receive in satisfaction of such share so much only of the estate as, when added to the value of the property, is sufficient, as nearly as can be estimated, to make up the full amount of that share.

(5) This section shall apply only to a provision made before the commencement of this Act.