(1) Where a person, having a limited interest in possession in property (in this section referred to as the first-mentioned interest), takes a further interest (in this section referred to as the second-mentioned interest) in the same property, as a taxable gift or a taxable inheritance, in consequence of which that person becomes the absolute owner of the property, the taxable value of the taxable gift or taxable inheritance of the second-mentioned interest at the valuation date is reduced by the value at that date of the first-mentioned interest, taking such value to be the value, ascertained in accordance with the Rules contained in Schedule 1, of a limited interest which -

(a) is a limited interest in a capital sum equal to the value of the property,

(b) commences on that date, and

(c) is to continue for the unexpired balance of the term of the first-mentioned interest.