Where, by a contract made at any time, the right to dispose of any property has been excluded or restricted, then, in determining the value of the property for the purpose of the first relevant event happening after that time,—
the exclusion or restriction shall be taken into account only to the extent (if any) that consideration in money or money's worth was given for it, but
if the contract was a chargeable transfer or was part of associated operations which together were a chargeable transfer, an allowance shall be made for the value transferred thereby (calculated as if no tax had been chargeable on it) or for so much of the value transferred as is attributable to the exclusion or restriction.
Where the contract was made before 27th March 1974 subsection (1) above applies only if the first relevant event is a transfer made on death.
In this section "relevant event", in relation to any property, means—
a chargeable transfer in the case of which the whole or part of the value transferred is attributable to the value of the property; and
anything which would be such a chargeable transfer but for this section.