(1) A testamentary disposition shall be valid as regards form if its form complies with the internal law -

(a) of the place where the testator made it, or

(b) of a nationality possessed by the testator, either at the time when he made the disposition, or at the time of his death, or

(c) of a place in which the testator had his domicile either at the time when he made the disposition, or at the time of his death, or

(d) of the place in which the testator had his habitual residence either at the time when he made the disposition, or at the time of his death, or

(e) so far as immovables are concerned, of the place where they are situated.

(2) Without prejudice to subsection (1), a testamentary disposition revoking an earlier testamentary disposition shall also be valid as regards form if it complies with any one of the laws according to the terms of which, under that subsection, the testamentary disposition that has been revoked was valid.

(3) For the purposes of this Part, if a national law consists of a non-unified system, the law to be applied shall be determined by the rules in force in that system and, failing any such rules, by the most real connexion which the testator had with any one of the various laws within that system.