17.— Section 16 applies to any interest in property whenever created but does not apply if, before the commencement of this Part, in reliance on such an interest being invalid by virtue of the application of any of the rules abolished by that section—

(a) the property has been distributed or otherwise dealt with, or

(b) any person has done or omitted to do any thing which renders the position of that or any other person materially altered to that person’s detriment after the commencement of this Part.